Brood Parasites and Cheating Species

"The exact route to brood parasitism is unclear." — Harry F. Sanders III, Answers in Genesis, 2024¹

"This depression seems formed by nature for the design of giving a more secure lodgement to the egg of the Hedge-sparrow, or its young one" — Edward Jenner, on the newly hatched cuckoo's back, 1788²

Summary

Brood parasites are the hardest case in this series for any account that treats parasites as damaged versions of harmless ancestors. A brood parasite gets another species to raise its young. Its tools work. Real losses exist and can be counted, but each one comes after the parasitic habit, not before it.

The young-earth position, in its own words. Answers in Genesis calls the cowbird "a sobering case of the curse on creation" whose design is "used for devious purposes." Creation Ministries International calls brood parasitism "a byproduct of the Curse." The fullest treatment, by Harry Sanders in 2024, says it "must have arisen in the aftermath of the fall," that for cowbirds "the behavior arose post-flood," and that "the exact route to brood parasitism is unclear." No young-earth source found discusses cuckoo bees, cuckoo wasps or slave-making ants.³³⁴¹¹¹
How often it arose. Obligate brood parasitism arose seven separate times in birds, in about 100 species, or 1% of all birds. It is known in one fish, the cuckoo catfish. It arose four times in one bee family, where 28% of species are parasites. Half of the 172 Formica ant species are confirmed or suspected social parasites.⁵⁶⁷⁸
Relatives and halfway cases are alive today. Most cuckoo species raise their own young. Two American cuckoos build nests and also lay in the nests of 10 and 11 other species. Wood ducks and hooded mergansers do the same to each other. Formica sanguinea takes slaves but can live without them. Honeyguides are the exception: all 17 species are parasites.⁹¹⁰¹¹¹²¹³
The equipment is a gain. The cuckoo chick hatches with a hollow in its back that fits an egg and fills in within twelve days. The honeyguide chick hatches blind with hooks on its bill and kills its nest-mates within hours. Egg colour that copies the host passes from mother to daughter in the cuckoo finch and in blue-egg cuckoos.²¹⁴¹⁵¹⁶
The arms race has numbers. Hosts reject odd eggs at rates from 2% in dunnocks to 67% in garden warblers, and cuckoo eggs copy best where rejection is strongest. Kirtland's warbler nests were parasitised by cowbirds at 48% to 86% before trapping began in 1972 and at 3.4% after.¹⁷¹⁸¹⁸
Hosts that never meet the parasite lose part of their egg defence in one or two centuries and keep their rejection behaviour.¹⁹²⁰
Where a loss model has something to measure, it passes, and it explains little. Amazon ant workers scored zero for foraging and brood care in a laboratory count. Slave-making ants have half the taste receptors of their hosts. But the raid, the hooks and the mimicry are not losses, and workerless parasitic ants lost a whole caste with "strikingly little evidence of gene loss."²¹²²²³
Verdict. Nothing in the parasite's toolkit looks broken. A corruption model can describe what these animals stopped doing. It has no account of what they started doing.

Sibling articles cover parasitoid wasps, behaviour-manipulating parasites, ticks, fleas, lice, mites and botflies and parasitic plants and fungi.

Part 1: What young-earth writers propose

Five young-earth sources on brood parasites were found. Three are short magazine pieces. One is a long article. One is a classification of bird kinds.

Tom Hennigan, writing for Answers in Genesis in 2020, puts the cowbird under the curse and keeps its abilities under design: "This bird is still a source of wonder because its design and intelligence, despite being used for devious purposes, are the products of a creative Genius." He looks forward to "a day when cowbirds will lay eggs in their own nest." That implies the original cowbird nested. He gives no account of the change.³³

Sanders calls Jon Ahlquist "the late great creationist ornithologist." In Creation magazine in 2020 Ahlquist described gentes, the chick's hollow back and the honeyguide's hooks accurately, called the habit "a byproduct of the Curse," and added: "Evolutionists have no idea of the origin of brood parasitism." He set aside the birds that parasitise only sometimes: "we do not consider them here." He offered no origin account of his own.⁴⁴¹

Harry Sanders's 2024 article for Answers in Genesis is the only one that reasons about origin. His position has four parts. Brood parasitism "almost certainly did not exist, at least in its current form, before the fall." For cowbirds, "other members of the kind do not share its lifestyle, making it likely that the behavior arose post-flood." Host defences "could have been there from the beginning, though only implemented after the fall." And the route is unknown: "Beyond that, far more research is needed." He also asks the right question of the secular imprinting hypothesis: "Why was nest building lost in the parasite?"¹¹¹¹

An Institute for Creation Research piece from 2020 mentions the cuckoo's parasitism in one paragraph and gives no origin.²⁴

Jean Lightner's 2013 estimate of the bird kinds on the Ark sets most kinds at the family. All cuckoos are one kind of "nearly 150 species." Honeyguides are one kind. Cowbirds, indigobirds and the cuckoo finch fall inside one "Sparrow/Finch kind" of 1,471 species. She does not discuss parasitism as a problem. The consequence is not hers, but it follows from her boundaries: inside the cuckoo kind and the sparrow kind, parasitism arose after the Flood, as Sanders says of the cowbird.²⁵²⁵²⁵

The two general models used elsewhere in this series do not address this class. Joseph Francis's 2008 model names "genetic alteration of the original good microbe" and "displacement or movement of the microbe." Warren Shipton's 2019 model says "Parasitism arose through gene loss, the expression of front-loaded genes now facilitating pathological life cycles, or other scenarios." Neither paper mentions a bird, a bee or an ant.²⁶²⁷

Sorted by what each proposal supplies:

Case	Proposed earlier behaviour	Evidence offered
Cowbird, by Hennigan	Laying in its own nest, implied	None offered. Relatives that nest exist.
Birds in general, by Sanders	None named. Origin after the Fall by an unknown route	None. He rejects two secular routes.
Host egg rejection, by Sanders	Created, used only later	None offered. Coots reject eggs laid by other coots, which gives the ability a use without cuckoos.²⁸
Cuckoo catfish, by Sanders	"Must be learned, rather than instinctual"	Partly wrong. See Part 4.
Birds, by Ahlquist and by Johnson	None	None
Cuckoo bees, cuckoo wasps, slave-making ants	No young-earth source found	None

Part 2: How many times, and from what

Birds. Michael Sorenson and Robert Payne counted seven independent origins in 2002, and the count has held. Nan Lyu and colleagues list them in 2025: three in cuckoos with 65 parasitic species, one in cowbirds, one in the African family of indigobirds, whydahs and the cuckoo finch, one in honeyguides, and the black-headed duck. Peter Lowther of the Field Museum counts about 107 species.⁵¹²²⁹²⁹

Relatives. Oliver Krüger and Nicholas Davies wrote in 2002 that cuckoos "show the highest diversity of breeding strategies within one bird family (parental care, facultative and obligate brood parasites)." With 65 parasites among about 141 species, more than half of all cuckoos raise their own young. The five cowbirds sit among nesting blackbirds. Honeyguides are different. Their hooks and killing behaviour "are absent in their non-parasitic relatives, the woodpeckers (Picidae) and barbets (Capitonidae)," and no honeyguide is known to nest.¹⁰¹⁴¹⁵

Halfway cases. Darwin built his cuckoo argument on one. He supposed "that the ancient progenitor of our European cuckoo had the habits of the American cuckoo; but that occasionally she laid an egg in another bird's nest." He then had to report that the American cuckoo does no such thing: "I hear on the high authority of Dr. Brewer, that this is a mistake." Brewer was wrong. Janice Hughes reported in 1997 that black-billed and yellow-billed cuckoos "are facultative brood parasites that occasionally lay their eggs in the nests of 10 and 11 other bird species, respectively." Ducks supply another case. In 1,750 wood duck nests and 377 hooded merganser nests, about 13% and 24% held eggs of the other species. American coots lay in each other's nests, and the victims reject enough eggs to cut the cost by half.³⁰³⁰⁹²⁸¹³

A halfway case shows that the step is possible for a living bird. It does not show that any obligate parasite took it. Lyu's team, who favour an evolutionary origin, call it "one of the most compelling unsolved puzzles in evolutionary biology." Hughes even suggests that the American cuckoos descend from an obligate parasite and partly returned to nesting, which would run the other way.⁹²⁹

Cowbirds. Scott Lanyon's 1992 tree has parasitism arise once in the blackbirds, with the specialist first: "host-specificity, with host-generality representing the derived condition." The numbers fit. The screaming cowbird has 5 known hosts. The brown-headed cowbird has been found in the nests of 248 species, and 173 of them have raised its young. Hennigan gives "as many as 220" and Sanders "over 100"; the current list is longer than either.³¹³¹²¹²¹

Fish. The cuckoo catfish of Lake Tanganyika is "the only obligate nonavian vertebrate brood parasite." It lays among spawning cichlids that carry their eggs in the mouth. Its young "hatch earlier than cichlids and prey on the developing cichlid embryos inside their mother’s buccal cavity." Sanders notes that its relatives spawn on the lake bed and use no host.⁷⁷¹

Bees and wasps. Sophie Cardinal's 2010 tree of the bee family Apidae found that brood parasitism "has arisen just four times," and that 99% of the parasitic species form one group. Cuckoo wasps do the same to hunting wasps: the larva of Hedychrum rutilans "kills the beewolf larva and feeds on it and the bees."³²⁶

Part 3: The equipment

The cuckoo chick. Edward Jenner watched a newly hatched cuckoo work a hedge-sparrow chick onto its back, climb the nest wall backward and throw it out. He described the anatomy in 1788: "its back from the scapulae downwards is very broad, with a considerable depression in the middle." The hollow is temporary. "When it is about twelve days old, this cavity is quite filled up." Modern fieldwork in Hungary found that eviction starts "on average 2 days after hatching" and that it costs the chick growth, which it later recovers. The chick is blind and naked when it does this.²²²³³³³

The honeyguide chick. Claire Spottiswoode and Jeroen Koorevaar filmed greater honeyguides in bee-eater burrows in Zambia. The chick hatches at about 3 grams with bill hooks already formed. "Despite being blind and in total darkness, honeyguides attacked host young with sustained biting, grasping and shaking motions." One to five minutes of attack was enough to kill. The hooks are not shed, as Ahlquist says. They "grow gradually into the growing bill."¹⁴¹⁴¹⁴⁴

Egg mimicry, and how it is inherited. One cuckoo species lays brown spotted eggs in pipit nests and plain blue eggs in redstart nests. Males mate with females of any race, so the races should blend. The old answer was that egg colour sits on the W chromosome, which only females carry. The evidence is narrower than the usual summary.

In 2000, Lisle Gibbs found that the races differ "in maternally inherited mitochondrial DNA, but not in microsatellite loci of nuclear DNA."³⁴
In 2011, Frode Fossøy found nuclear differences too, in Bulgaria, and concluded that the egg genes "may be found on autosomal chromosomes rather than the female-specific W-chromosome as previously assumed."³⁵
In 2016, Fossøy's team reported "the first unambiguous evidence for maternal inheritance of egg colouration," for blue eggs only. They added: "Whether other egg colours and spotting patterns in European common cuckoos are maternally inherited remains an open question."¹⁵¹⁵
In 2022, Spottiswoode's team showed that in the African cuckoo finch, "host-specific egg mimicry" is "maternally inherited." The same inheritance now holds the parasite back. Its hosts mix genes from two parents and have produced olive-green eggs that the cuckoo finch cannot copy.¹⁶¹⁶

So egg mimicry does track the host down the female line. That is shown for one egg type in one cuckoo and for the cuckoo finch. No one has named the gene.

Insects copy smell. Cuckoo bees "lack pollen-collecting structures, and they are often heavily armored." In most, "a specialized larval instar kills the host larva." Darwin thought this "more remarkable than that of the cuckoo; for these bees have not only their instincts but their structure modified." The cuckoo wasp Hedychrum rutilans wears the skin chemistry of its host. Beewolves treated paper carrying its scent no differently from paper carrying solvent alone.³⁰³²⁶⁶

Cowbirds enforce. Jeffrey Hoover and Scott Robinson removed cowbird eggs from warbler nests in Illinois. Of those nests, 56% were then destroyed, against 6% of nests that kept the cowbird egg. "No nests were destroyed when cowbird access was always denied."³⁶³⁶

Every item in this part is something added: a structure, a timed behaviour, a colour, a scent. The cuckoo bee's missing pollen brush is the one loss, and it is what a bee that gathers no pollen would be expected to lack.

Part 4: The arms race, with numbers

Rejection and mimicry rise together. Mary Caswell Stoddard and Martin Stevens measured egg pattern in eight cuckoo hosts as a bird's eye sees it. Dunnocks reject odd eggs at 2% to 6%, and the cuckoo's egg in a dunnock nest copies nothing. Meadow pipits reject at 18% to 48%, reed warblers at 31% to 62%, garden warblers at 67%. Across the eight, "cuckoos have evolved better pattern mimicry for host species that exhibit stronger egg rejection." In Zambia, three hosts of the cuckoo finch rejected 63 of 125, 33 of 59 and 23 of 37 foreign eggs.¹⁷¹⁷¹⁷¹⁷¹⁷³⁷

The fish shows the same pattern. Cichlids that live with the cuckoo catfish rejected 90% of its eggs within a day. Cichlids from a lake without it rejected 7%. The defence has a price: the experienced hosts also threw out more of their own eggs. The catfish improves with practice, from 13% of host clutches parasitised by beginners to 25% and 29% by experienced fish. That answers Sanders's claim that the behaviour "must be learned, rather than instinctual." Beginners already do it. Practice makes them better at it.⁷⁷³⁸¹

Not every pair is racing. The Cape bulbul accepts a Jacobin cuckoo egg twice the size of its own. Krüger's model finds that acceptance is the bulbul's best option, because the egg is too big to eject and deserting costs more. The large-billed gerygone of Australia has no egg defence and instead drags the cuckoo chick out of the nest. Sanders argues against the usual "evolutionary lag" explanation that dunnocks have been cuckoo hosts for 600 years and still do not reject, and he calls the delay "ludicrous." The point is fair against lag. Krüger's result is the secular alternative.³⁹⁴⁰⁴⁰¹

Hosts that never meet the parasite. Two tests exist, and they give different answers for different traits.

Egg appearance decays. African village weavers lay eggs that differ greatly from hen to hen and hardly at all within a clutch, which makes a cuckoo's copy easy to spot. Weavers were taken to Hispaniola before the 1790s and to Mauritius in 1886. Neither island has an egg-copying cuckoo. David Lahti found that on both islands the variation between hens and the consistency within a clutch had fallen, more on Hispaniola. Spotted clutches fell from 74% to 78% in Africa to 58% and 64%. Lahti allows that founder effect and drift may have contributed.¹⁹¹⁹¹⁹
Rejection behaviour stays. Bohemian waxwings breed north of the cowbird's range. Brian Peer's team put cowbird eggs in nine nests, and all nine pairs threw them out. Cedar waxwings, which live with cowbirds, reject 69%. Nine nests is a small sample.²⁰²⁰

A behaviour that costs nothing until a strange egg appears is kept. An egg pattern that must be maintained in every clutch drifts. The weaver result also shows that measurable change in a defence can take less than 120 years, which matters for any young-earth timescale.

The cost to a host with no defence. Kirtland's warbler nests in young jack pine in Michigan. "Between 1903 and 1971, observed parasitism rates of Kirtland’s warbler nests ranged from 48 percent to 86 percent," and nests fledged fewer than one young each. Cowbird trapping began in 1972. Parasitism "averaged 3.4 percent between 1972 and 1981," and fledging rose to 2.8 per nest. In 2015 one nest in 157 was parasitised.¹⁸¹⁸¹⁸¹⁸

The population did not follow at once. It was about 201 singing males in 1971 and "remained relatively stable at approximately 200 singing males" for the next 18 years. It rose in the 1990s as habitat was restored, to 2,383 in 2015. Trapping stopped the fall. It did not by itself produce the recovery, so Hennigan's statement that the programme "greatly increased the warbler population" claims too much.¹⁸¹⁸³

Part 5: Slave-making ants and what the genomes show

What Darwin reported. Darwin gave the Amazon ant, now Polyergus rufescens, as his extreme case, from Pierre Huber's experiment: "when Huber shut up thirty of them without a slave, but with plenty of the food which they like best, and with their larvæ and pupæ to stimulate them to work, they did nothing; they could not even feed themselves, and many perished of hunger." One slave put in with them fed the survivors. He set Formica sanguinea beside it, which keeps far fewer slaves and does its own work.³⁰

What has been measured since. Joshua King and James Trager logged every act in a laboratory colony of Polyergus lucidus and its Formica slaves. The slaves performed 1,727 acts. The Polyergus workers performed 124, mostly self-grooming, aggression and scouting. They scored zero for foraging, fetching food, and carrying, grooming or feeding brood. They were 12% to 20% of the workers. A 2025 genome paper puts it in one sentence: "these species have lost the ability to perform most typical worker ant behaviors, including foraging, nest excavation, and brood care."²¹²¹⁴¹

This is the one place in the article where something is plainly missing. What remains is not feeble. The worker still scouts, raids and fights, with sickle jaws built for it.

The halfway case and the relatives. Slaves "increase the workforce" of a facultative slave-maker such as Formica sanguinea, while for an obligate one they are "vital for colony survival." Marek Borowiec's 2021 tree of Formica and Polyergus finds that slave-raiding arose once in Formica, in a lineage that already founded its colonies inside other species' nests. Ant parasites and their hosts "are close relatives," which is called Emery's rule. On a young-earth reading that probably puts raider and victim in one created kind, so the habit arose inside the kind. No young-earth classification of ants was found to confirm it.¹¹⁸⁸

Darwin declined to guess how raiding began and then guessed: "pupæ originally stored as food might become developed; and the ants thus unintentionally reared would then follow their proper instincts." That is still one of three live hypotheses. Borowiec's team favours it and concedes that the benefit has never been shown: "we are not aware of experimental studies demonstrating fitness benefits provided by stolen host workers to facultatively dulotic species."³⁰³⁰⁸

Hosts fight back. Where raids by Temnothorax americanus are common, its hosts defend better and the raiders raid better. Enslaved workers of three host species killed two-thirds of the slave-maker's female pupae.⁴²⁴³

The genomes. Here the loss model can be tested gene by gene.

Study	Parasites compared	Result
Jongepier 2022	3 slave-making ants, 3 origins	Taste receptors 41 to 52, against 91 to 128 in hosts. Smell receptors down 25% to 30%. 18 of 307 smell receptor groups lost in all three²³²³²³
Schrader 2021	3 workerless leaf-cutter parasites	Smell receptors down by 32, by 38, and from 467 to 263. No matching loss in four other gene families⁴⁴⁴⁴
Smith 2015	3 workerless parasites, 2 origins	"strikingly little evidence of gene loss" though the worker caste is gone²²
Feldmeyer 2017	3 slave-making ants	309 genes changed under selection in slave-makers, 161 in hosts, few shared⁴⁵
Osipova 2026, abstract only	5 brood-parasitic birds, 3 origins	Changes in sperm and nerve genes. No loss reported⁴⁶

The losses are real, repeated and confined. Evelien Jongepier's team read them as following the behaviour: the missing taste receptors are "potentially mirroring the outsourcing of foraging tasks to host workers." Lukas Schrader's team attribute theirs to "relaxed selective constraints." An ant that no longer forages stops maintaining the genes for finding food. In birds, a 2025 preprint with genomes of ten brood parasites says "little is known about the genetic basis" of the habit. So the catalogue phrase "no genome to lose" is true of birds as far as anyone has yet looked, and false of ants.⁴⁴²³⁴⁷

Objections and responses

The Curse explains it. Hennigan, Ahlquist and Sanders all say so. As theology that is outside this article. As biology it names a time, not a mechanism. Sanders concedes this. A claim that names no earlier behaviour and no change cannot be checked against a genome or a nest.

"Evolutionists have no idea of the origin of brood parasitism." Ahlquist overstates a real weakness. Lyu's team call the origin an unsolved puzzle, and Borowiec's team admit that the benefit of part-time slave-raiding has never been measured. But secular work has living halfway cases, family trees and testable models. Ahlquist set the halfway cases aside. Sanders rejects same-species parasitism as a stepping stone and so removes the most obvious harmless precursor from his own side as well.⁴⁴

Parasitic and nesting cuckoos are one kind, so the habit had to arise in about 4,500 years, which is impossible. This is the strongest objection to the young-earth account, and Sanders accepts its premise for cowbirds. Fast change in a host defence is documented, in under 120 years on Mauritius. That was decay of variation. No one has watched an eviction hollow, a bill hook or an egg colour arise. The young-earth side has not answered this. Shipton's "front-loaded genes" would answer it only by making the parasitic equipment part of the original creation.²⁷

Gene loss in slave-making ants confirms degeneration. It confirms that loss happened. The authors who measured it place it after the parasitic habit began, and Smith's workerless ants lost a caste while keeping the genes. A loss model that starts from the loss has the order backwards.

A chick that kills its nest-mates refutes a good designer. Darwin argued this way. It was "far more satisfactory" to see "the young cuckoo ejecting its foster-brothers" as "small consequences of one general law" than as "specially endowed or created instincts." That is an argument about what God would do. This article tests a narrower claim, whether these animals look damaged. The theology is treated in Death Before the Fall.³⁰

Host defences were created ready for use. Sanders's suggestion fits two results. Coots use egg recognition against other coots, so the ability has work to do without cuckoos. Waxwings keep rejection where no parasite lives. Neither result separates his account from a secular one, since both predict that a free defence is kept.

Issues and unanswered questions

No young-earth source addresses cuckoo bees, cuckoo wasps or slave-making ants. The class with the best loss data has no creationist account at all.
No earlier harmless use has been proposed for the cuckoo chick's back, the honeyguide's hooks or mimetic eggs. Calling them design "used for devious purposes" concedes that the structures were made for something, and nothing else they could be for has been suggested.
If kinds are families, parasitism arose after the Flood three times in the cuckoo kind alone. No young-earth paper has priced that.
The gene behind any cuckoo egg colour is unidentified. Maternal inheritance is shown for blue eggs and for the cuckoo finch only, and Gibbs and Fossøy disagree on nuclear markers.
Seven sources were read as abstracts only: Sorenson and Payne 2002, Gibbs 2000, Lanyon 1992, Lyon 2003, Achenbach and Foitzik 2009, Hughes 1997 and Osipova 2026. Davies and Brooke's 1989 rejection rates are cited through Stoddard and Stevens. Kelly and DeCapita's 1982 warbler figures are cited through the Federal Register.
Peer's waxwing test rests on nine nests. Lahti's weaver result may include founder effect.
The dates in the secular papers for these origins, from about 2 to over 30 million years, come from molecular clocks and are not used here.

Verdict

The catalogue description said that nothing here looks broken. For the parasite's working parts that is correct. The cuckoo chick's back, the honeyguide's hooks, host-matched egg colour, the cuckoo wasp's borrowed scent and the Amazon ant's raid are additions, each fitted to a task.

The description also said there is no genome to lose. That is wrong for ants. Slave-making ants have lost about half their taste receptors and a quarter of their smell receptors, and Polyergus workers no longer forage, dig or nurse. These are the measurable losses a corruption model predicts. They come after dependence, and they explain why the parasite cannot leave its host, not how it came to have one.

Young-earth writers have not claimed otherwise. They call the behaviour cursed and the abilities designed, place the origin after the Fall, and say the route is unknown. That is an honest statement of the position, and it leaves this class without a young-earth explanation. The secular account has living halfway cases and no demonstrated pathway either.

Sources

1.
Sanders, Harry F. III. “Brood Parasitism.” Answers in Depth. Jan 12, 2024. Retrieved Sep 29, 2026. Answers in Genesis staff writer. Read from the downloaded page; quotations located by section heading. Copyright.
1. 1a.
  Section Brood Parasitism and the Fall: “It almost certainly did not exist, at least in its current form, before the fall.” ↩
2. 1b.
  Section Brood Parasitism and the Fall: “Like carnivory, brood parasitism must have arisen in the aftermath of the fall.” ↩
3. 1c.
  Section Brood Parasitism and the Fall: “The exact route to brood parasitism is unclear.” ↩ ↩
4. 1d.
  Section Brood Parasitism and the Fall: “In the case of the cowbird, other members of the kind do not share its lifestyle, making it likely that the behavior arose post-flood.” ↩ ↩
5. 1e.
  Section Brood Parasitism and the Fall: “The responses to brood parasitism, particularly egg rejection and teaching begging calls to the chicks, could have been there from the beginning, though only implemented after the fall. Beyond that, far more research is needed.” ↩
6. 1f.
  Section Where Did It Come From?: “Why was nest building lost in the parasite? Imprinting did not do that.” ↩
7. 1g.
  Section Brood Parasitism: Fish: “Particularly in the cuckoo example, the brood parasitic behavior must be learned, rather than instinctual.” ↩
8. 1h.
  Section Brood Parasitism: Fish: “Other members of the genus are substrate spawners and do not use cichlids or any other fish as hosts for their eggs.” ↩
9. 1i.
  Section Where Did It Come From?: “Put candidly by the late great creationist ornithologist Jon Ahlquist”. ↩
10. 1j.
  Section Interspecific Brood Parasitism: Birds: “Cowbirds, among the most common species of brood parasites, are known to have over 100 potential hosts.” ↩
11. 1k.
  Section Interspecific Brood Parasitism: Birds: “the idea that it would take more than 600 years to adapt to a parasite is ludicrous”. ↩
2.
Jenner, Edward. “Observations on the Natural History of the Cuckoo. By Mr. Edward Jenner. In a Letter to John Hunter, Esq. F. R. S.” Philosophical Transactions of the Royal Society of London 78:219–237. 1788. Read from the page images of the archive.org scan. The page number was read from the running head. The long s is written as s and scapulæ as scapulae. Public domain.
1. 2a.
  Page 225: “The little animal, with the assistance of its rump and wings, contrived to get the bird upon its back, and making a lodgement for the burden, by elevating its elbows, clambered backward with it up the side of the nest till it reached the top, where resting for a moment, it threw off its load with a jerk, and quite disengaged it from the nest.” ↩
2. 2b.
  Page 226: “its back from the scapulae downwards is very broad, with a considerable depression in the middle. This depression seems formed by nature for the design of giving a more secure lodgement to the egg of the Hedge-sparrow, or its young one”. ↩ ↩
3. 2c.
  Page 226: “When it is about twelve days old, this cavity is quite filled up, and then the back assumes the shape of nestling birds in general.” ↩ ↩
3.
Hennigan, Tom. “Cowbirds—Passing on Parenthood.” Answers. Oct 1, 2020. Retrieved Sep 29, 2026. Answers in Genesis magazine, October–December 2020. The author teaches biology at Truett McConnell University. Read from the downloaded page; quotations located by section heading. Copyright.
1. 3a.
  Section introduction, before Criminal Activity: “But while the cowbird’s behavior is a sobering case of the curse on creation, its intelligence is a tribute to the brilliant Creator.” ↩
2. 3b.
  Section Bad Eggs?: “This bird is still a source of wonder because its design and intelligence, despite being used for devious purposes, are the products of a creative Genius.” ↩ ↩
3. 3c.
  Section Bad Eggs?: “a day when cowbirds will lay eggs in their own nest”. ↩
4. 3d.
  Section Sacrifice or Survival: “Amazingly, mama cowbirds may parasitize the nests of as many as 220 different species of birds.” ↩
5. 3e.
  Section Did You Know: “The state of Michigan’s cowbird removal program greatly increased the warbler population.” ↩
4.
Ahlquist, Jon. “Avian deceptions.” Creation 42(3):54–55. Jul 2020. Retrieved Sep 29, 2026. Creation Ministries International. Posted on the web 5 September 2021. Read from the downloaded web page, so quotations are located by paragraph, not by printed page. Copyright.
1. 4a.
  Paragraph 1: “This freeloading behaviour is a byproduct of the Curse on nature following mankind’s sin (Genesis 3:17–18; Romans 8:19–22).” ↩
2. 4b.
  Paragraph 2: “Others occasionally practise the behaviour (facultative brood parasites), but we do not consider them here.” ↩ ↩
3. 4c.
  Section before Fighting back: “are hatched with deciduous (temporary) hooks on each jaw”. ↩
4. 4d.
  Section final paragraph: “Evolutionists have no idea of the origin of brood parasitism. Their speculations and ‘just-so stories’ simply do not make a plausible account.” ↩ ↩
5.
Sorenson, Michael D., and Robert B. Payne. “Molecular Genetic Perspectives on Avian Brood Parasitism.” Integrative and Comparative Biology 42(2):388–400. 2002. Abstract only, from the PubMed record. The publisher's copy could not be downloaded. Copyright.
1. 5a.
  Section abstract: “Recent molecular systematics studies indicate that obligate brood parasitism has evolved independently in seven different avian lineages”. ↩ ↩
6.
Cardinal, Sophie et al. “Comprehensive phylogeny of apid bees reveals the evolutionary origins and antiquity of cleptoparasitism.” Proceedings of the National Academy of Sciences 107(37):16207–16211. 2010. Covers the family Apidae only. Parasitism also occurs in other bee families, which were not counted here. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 6a.
  Page 16207: “we show that cleptoparasitism has arisen just four times in Apidae, which is fewer times than previously estimated. Our results indicate that 99% of cleptoparasitic apid bees form a monophyletic group.” “cleptoparasitic species (28%) and tribes (50%)”. ↩ ↩
2. 6b.
  Page 16207: “they lack pollen-collecting structures, and they are often heavily armored relative to pollen-collecting species”. ↩
3. 6c.
  Page 16207: “In a few cases, the adult female parasite destroys the host egg (13), but more commonly, a specialized larval instar kills the host larva (14).” ↩
7.
Blažek, Radim et al. “Success of cuckoo catfish brood parasitism reflects coevolutionary history and individual experience of their cichlid hosts.” Science Advances 4(5):eaar4380. May 2, 2018. Publisher PDF from PubMed Central. CC BY-NC. Mirror: PMC
1. 7a.
  Page 1: “the only obligate nonavian vertebrate brood parasite, the cuckoo catfish Synodontis multipunctatus”. ↩ ↩
2. 7b.
  Page 1: “Catfish offspring hatch earlier than cichlids and prey on the developing cichlid embryos inside their mother’s buccal cavity”. ↩
3. 7c.
  Page 2: “The rejection of cuckoo catfish eggs over the first 24 hours by sympatric Tanganyikan S. diagramma females (90%; Fig. 1A) was dramatically higher than rejections by Haplochromis aeneocolor from Lake George (evolutionarily naïve to cuckoo catfish) [7%”. ↩
4. 7d.
  Page 1: “a high rejection frequency of parasitic catfish eggs by coevolved sympatric hosts came at a cost of increased rejection of their own eggs”. ↩
8.
Borowiec, Marek L. et al. “The evolution of social parasitism in Formica ants revealed by a global phylogeny.” Proceedings of the National Academy of Sciences 118(38):e2026029118. 2021. Publisher PDF from PubMed Central; pages are numbered 1 to 10. CC BY-NC-ND. Mirror: PMC
1. 8a.
  Page 1: “half of its 172 species are confirmed or suspected social parasites, which includes all three major classes of social parasitism known in ants”. ↩
2. 8b.
  Page 1: “Entomologists have long noticed that ant social parasites and their hosts are close relatives”. ↩
3. 8c.
  Page 6: “dulosis evolved secondarily from a temporary socially parasitic ancestor”. ↩
4. 8d.
  Page 6: “we are not aware of experimental studies demonstrating fitness benefits provided by stolen host workers to facultatively dulotic species”. ↩
9.
Hughes, Janice M. “Taxonomic significance of host-egg mimicry by facultative brood parasites of the avian genus Coccyzus (Cuculidae).” Canadian Journal of Zoology 75(9):1380–1386. 1997. Abstract only, from the OpenAlex record. Full text not obtained. Copyright.
1. 9a.
  Section abstract: “Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) cuckoos are facultative brood parasites that occasionally lay their eggs in the nests of 10 and 11 other bird species, respectively.” ↩ ↩
2. 9b.
  Section abstract: “This hypothesis is corroborated by recent phylogenetic analyses which suggest that the ancestral Coccyzus was an obligate parasite.” ↩
10.
Krüger, Oliver, and Nicholas B. Davies. “The evolution of cuckoo parasitism: a comparative analysis.” Proceedings of the Royal Society B 269(1489):375–381. 2002. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 10a.
  Page 375: “Cuckoos (family Cuculidae) show the highest diversity of breeding strategies within one bird family (parental care, facultative and obligate brood parasites).” “The ancestral state was probably tropical, resident, forest cuckoos with parental care.” ↩ ↩
11.
Czechowski, W., and E. J. Godzińska. “Enslaved ants: not as helpless as they were thought to be.” Insectes Sociaux 62:9–22. 2015. Review. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 11a.
  Page 9: “Whereas slaves of facultative slave-makers increase the workforce of the colony, in obligate”. “presence of slaves is vital for colony survival.” The word between the two pieces is slave-makers, which the printed abstract breaks across two lines. The sentence is continuous. Page 12 names Formica sanguinea as a facultative slave-maker. ↩ ↩
12.
Lowther, Peter E. Lists of victims and hosts of the parasitic cowbirds (Molothrus). Field Museum, Chicago. Oct 16, 2023. A working list kept by the museum's ornithologist. A victim is a species found with a cowbird egg; a host is one known to have raised a cowbird. Licence not stated.
1. 12a.
  Page 1: “About 1% of all bird species are brood parasites which include of about 107 species found among five taxonomic groups”. The wording "include of" is the original's. ↩
2. 12b.
  Page 1: “the honeyguides (family Indicatoridae) of Africa and southern Asia (of which all 17 species are known or thought to be brood parasitic)”. ↩
3. 12c.
  Page 3, table Summary counts of victims and hosts of the brood parasitic cowbirds: “Brown-headed Cowbird Molothrus ater 248 173”. ↩
4. 12d.
  Page 3, table Summary counts of victims and hosts of the brood parasitic cowbirds: “Screaming Cowbird Molothrus rufoaxillaris 5 5”. ↩
13.
Bakner, Dylan L. et al. “Wood ducks and hooded mergansers as interspecific brood parasites: An evaluation of parasitic egg survival.” Ecology and Evolution 14(7):e11721. 2024. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 13a.
  Page 1: “we monitored 1750 wood duck and 377 hooded merganser nests; ~13% of wood duck and ~24% of hooded merganser nests were interspecifically parasitized”. ↩ ↩
14.
Spottiswoode, Claire N., and Jeroen Koorevaar. “A stab in the dark: chick killing by brood parasitic honeyguides.” Biology Letters 8(2):241–244. 2012. Published online 7 September 2011. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 14a.
  Page 241: “these intriguing morphological and behavioural adaptations that are absent in their non-parasitic relatives, the woodpeckers (Picidae) and barbets (Capitonidae)”. ↩
2. 14b.
  Page 241: “Despite being blind and in total darkness, honeyguides attacked host young with sustained biting, grasping and shaking motions.” ↩ ↩
3. 14c.
  Page 241: “was sufficient to cause host death, which took from 9 min to over 7 h from first attack”. Page 242: “honeyguides weighed ca 3 g, possessed fully developed bill hooks”. ↩
4. 14d.
  Page 243: “Hooks do not appear to be shed (cf. [4]), but rather grow gradually into the growing bill”. ↩
15.
Fossøy, Frode et al. “Ancient origin and maternal inheritance of blue cuckoo eggs.” Nature Communications 7:10272. Jan 12, 2016. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 15a.
  Page 1: “Here we report the first unambiguous evidence for maternal inheritance of egg colouration in the brood-parasitic common cuckoo Cuculus canorus.” ↩ ↩
2. 15b.
  Page 4: “Whether other egg colours and spotting patterns in European common cuckoos are maternally inherited remains an open question.” ↩
3. 15c.
  Page 4, figure 4: “comprehensive cuculiform data set representing 119 of 141 recognized cuckoo species”. ↩
16.
Spottiswoode, Claire N. et al. “Genetic architecture facilitates then constrains adaptation in a host–parasite coevolutionary arms race.” Proceedings of the National Academy of Sciences 119(17):e2121752119. 2022. Publisher PDF from PubMed Central. CC BY-NC-ND. Mirror: PMC
1. 16a.
  Page 1: “We demonstrate that host-specific egg mimicry in the African cuckoo finch Anomalospiza imberbis is maternally inherited, confirming the validity of an almost century-old hypothesis.” ↩ ↩
2. 16b.
  Page 1: “The inability to generate novel genetic combinations likely prevents cuckoo finches from mimicking certain host phenotypes that are currently favored by selection”. ↩
17.
Stoddard, Mary Caswell, and Martin Stevens. “Pattern mimicry of host eggs by the common cuckoo, as seen through a bird’s eye.” Proceedings of the Royal Society B 277(1686):1387–1393. 2010. The rejection rates are taken by the authors from Davies and Brooke 1989 and Avilés and Garamszegi 2007, which were not read. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 17a.
  Page 1387: “cuckoos have evolved better pattern mimicry for host species that exhibit stronger egg rejection”. ↩ ↩
2. 17b.
  Page 1389: “the dunnock, which rejects non-mimetic eggs at low rates ranging from 2 per cent (Avilés & Garamszegi 2007) to 6 per cent (Davies & Brooke 1989)”. Page 1391: “The cuckoo has no pattern mimicry where the hosts show no rejection”. ↩
3. 17c.
  Page 1389: “the meadow pipit, with moderate rejection rates between 18 per cent (Avilés & Garamszegi 2007) and 48 per cent (Davies & Brooke 1989)”. ↩
4. 17d.
  Page 1390: “warbler also has moderate egg rejection rates, from 31 per cent (Avilés & Garamszegi 2007) to 62 per cent (Davies & Brooke 1989)”. ↩
5. 17e.
  Page 1390: “garden warbler, with a high rejection rate of 67 per cent”. ↩
18.
U.S. Fish and Wildlife Service. “Endangered and Threatened Wildlife and Plants; Removing the Kirtland’s Warbler From the Federal List of Endangered and Threatened Wildlife.” Federal Register 84(196):54436–54463. Oct 9, 2019. Final rule. It cites Kelly and DeCapita 1982 and Walkinshaw 1972 for the figures, which were not read directly. Public domain.
1. 18a.
  Page 54451: “Between 1903 and 1971, observed parasitism rates of Kirtland’s warbler nests ranged from 48 percent to 86 percent”. ↩ ↩
2. 18b.
  Page 54451: “averaged 3.4 percent between 1972 and 1981”. ↩ ↩
3. 18c.
  Page 54451: “Kirtland’s warbler fledging rates simultaneously increased from less than one per nest to 2.8 per nest”. ↩
4. 18d.
  Page 54451: “In 2015, only one nest out of 157 was parasitized”. ↩
5. 18e.
  Page 54441: “By 1971, the Kirtland’s warbler population declined to approximately 201 singing males”. “remained relatively stable at approximately 200 singing males but experienced record lows of 167 singing males in 1974 and again in 1987”. ↩
6. 18f.
  Page 54441: “The population reached a record high of 2,383 singing males in 2015”. ↩
19.
Lahti, David C. “Evolution of bird eggs in the absence of cuckoo parasitism.” Proceedings of the National Academy of Sciences 102(50):18057–18062. 2005. Publisher PDF from PubMed Central; pages from the running foot. Copyright. Mirror: PMC
1. 19a.
  Page 18057: “In these two populations, between-individual variation and within-clutch consistency in egg appearance have both decreased, as has the incidence of spotting, relative to the source populations in Africa.” ↩ ↩
2. 19b.
  Page 18057: “introduced from Southern Africa to the island of Mauritius in a single event in 1886”. ↩
3. 19c.
  Page 18061: “Eggs of village weavers in Africa had spots in 74 –78% of clutches, but this declined to 58% on Mauritius and to 64% on Hispaniola.” ↩
20.
Peer, Brian D. et al. “Persistence of host defence behaviour in the absence of avian brood parasitism.” Biology Letters 7(5):670–673. 2011. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 20a.
  Page 670: “We found that egg rejection was expressed by 100 per cent of Bohemian waxwings.” The Results on page 671 give the sample as nine nests. ↩ ↩
2. 20b.
  Page 672: “Cedar waxwings reject 69 per cent of cowbird eggs”. ↩
21.
King, Joshua R., and James C. Trager. “Natural history of the slave making ant, Polyergus lucidus, sensu lato in northern Florida and its three Formica pallidefulva group hosts.” Journal of Insect Science 7(42). 2007. Publisher PDF from PubMed Central. CC BY 2.5. Mirror: PMC
1. 21a.
  Page 9, table 2: “Forage 50 (0.03) 0”. “Observed repertory size 1727 124”. The first number in each row is the Formica slaves' count and the last is the Polyergus workers' count. ↩ ↩
2. 21b.
  Page 9: “P. lucidus workers made up 12–20% of the number of workers (Table 1).” ↩
22.
Smith, Chris R. et al. “How Do Genomes Create Novel Phenotypes? Insights from the Loss of the Worker Caste in Ant Social Parasites.” Molecular Biology and Evolution 32(11):2919–2931. 2015. Publisher PDF from PubMed Central. CC BY-NC. Mirror: PMC
1. 22a.
  Page 2919: “the social parasites showed strikingly little evidence of gene loss, damaging mutations, or shifts in selection regime resulting from loss of the worker caste”. ↩ ↩
23.
Jongepier, Evelien et al. “Convergent Loss of Chemoreceptors across Independent Origins of Slave-Making in Ants.” Molecular Biology and Evolution 39(1):msab305. 2022. Published online 2021. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 23a.
  Page 1: “slave-making ant genomes harbored only half as many gustatory receptors as their hosts’, potentially mirroring the outsourcing of foraging tasks to host workers”. ↩ ↩
2. 23b.
  Page 3: “parasite range 41–52; host and nonhost range 91–128”. ↩
3. 23c.
  Page 3: “The percentage of Ors that were lost in each slave-making lineage was very similar, ranging from 25.08% in H. sublaevis to 27.69% in T. ravouxi and 29.97% in T. americanus”. ↩
4. 23d.
  Page 3: “In total, 18 out of 307 orthologous odorant receptor clusters showed convergent loss in the three slave-making ant species”. ↩
24.
Johnson, James J. S. “Cuckoo Completes Mammoth 7,500-Mile Migration.” Institute for Creation Research. Jun 2020. Retrieved Sep 29, 2026. News item. Its statement that the common cuckoo parasitises "like other cuckoos" is wrong for more than half of cuckoo species. Copyright.
1. 24a.
  Paragraph beginning How so?: “The common cuckoo, like other cuckoos, practices”. “meaning that it sneakily deposits its eggs into the nests of other birds”. The two pieces are joined in the original by the words brood parasitism in quotation marks. ↩
25.
Lightner, Jean K. “An Initial Estimate of Avian Ark Kinds.” Answers Research Journal 6:409–466. Nov 27, 2013. Read from the web page in the source library, so quotations are located by family heading. The cowbirds are in Icteridae, which she names. The indigobirds and cuckoo finch are in Viduidae, which she does not name but which falls inside her stated range of families. Copyright.
1. 25a.
  Section Cuculidae (The Cuckoo kind): “This family comprises nearly 150 species in over 30 genera (Gill and Donsker 2013).” ↩
2. 25b.
  Section Indicatoridae (The Honeyguide kind): “They have dull plumage and lay their eggs in the nests of other birds, especially small barbets and tinkerbirds.” ↩
3. 25c.
  Section Passeroidea (The Sparrow/Finch kind): “It is used in this work to include the families listed from Passeridae through Cardinalidae in the current IOC World Bird List (Gill and Donsker 2013).” “When the other families in this range are included, the total number of species rises to 1471.” ↩
26.
“Proceedings of the Microbe Forum, June 2007.” Answers Research Journal 1:1–6. Edited by Georgia Purdom and Joseph W. Francis. 2008. The quotation is from Joseph W. Francis's own abstract. Publisher PDF. Copyright.
1. 26a.
  Page 3: “the origin of microbial based disease has at least two primary causes, (1) post-Fall genetic alteration of the original good microbe and/or (2) post-Fall displacement or movement of the microbe from the site where it performed its beneficial function”. ↩
27.
Shipton, Warren A. “Destructive parasites: expressions of God’s creation?” Journal of Creation 33(2):84–92. 2019. Publisher PDF; abstract on the printed first page. Its examples are insects, malaria and filarial worms. Copyright.
1. 27a.
  Page 84: “Parasitism arose through gene loss, the expression of”. “genes now facilitating pathological life cycles, or other scenarios.” The word between the two pieces is front-loaded, which the printed abstract breaks across two lines. The sentence is continuous. ↩ ↩
28.
Lyon, Bruce E. “Egg recognition and counting reduce costs of avian conspecific brood parasitism.” Nature 422(6931):495–499. Apr 3, 2003. Abstract only, from the PubMed record. Full text is paywalled and was not obtained. Copyright.
1. 28a.
  Section abstract: “Hosts recognized and rejected many parasitic eggs, reducing the fitness costs of parasitism by half.” ↩ ↩
29.
Lyu, Nan et al. “A synthesized framework for the evolutionary origins of avian obligate brood parasitism.” Science Advances 11(47):eadx8063. Nov 19, 2025. Publisher PDF from PubMed Central. CC BY-NC. Mirror: PMC
1. 29a.
  Page 1: “how this remarkable strategy initially emerged and evolved remains one of the most compelling unsolved puzzles in evolutionary biology”. ↩
2. 29b.
  Page 10: “OBP has independently evolved three times among order Cuculiformes (cuckoos), which contains the greatest number of parasitic species (65 species).” ↩
3. 29c.
  Page 10: “OBP has also evolved twice among order Passeriformes (once in genus Molothrus in family Icteridae and once in family Viduidae), once among Piciformes (in family Indicatoridae), and once among Anseriformes (only in black-headed duck H. atricapilla).” ↩
30.
Darwin, Charles. On the Origin of Species by Means of Natural Selection. John Murray, London. 1st edition. 1859. Chapter VII, Instinct. Darwin Online transcription F373, which marks each printed page. Darwin's Polyerges rufescens is now Polyergus rufescens. Public domain.
1. 30a.
  Page 217: “Now let us suppose that the ancient progenitor of our European cuckoo had the habits of the American cuckoo; but that occasionally she laid an egg in another bird's nest.” ↩
2. 30b.
  Page 217: “It has been asserted that the American cuckoo occasionally lays her eggs in other birds' nests; but I hear on the high authority of Dr. Brewer, that this is a mistake.” ↩
3. 30c.
  Page 218: “This case is more remarkable than that of the cuckoo; for these bees have not only their instincts but their structure modified in accordance with their parasitic habits; for they do not possess the pollen-collecting apparatus which would be necessary if they had to store food for their own young.” ↩
4. 30d.
  Page 219: “So utterly helpless are the masters, that when Huber shut up thirty of them without a slave, but with plenty of the food which they like best, and with their larvæ and pupæ to stimulate them to work, they did nothing; they could not even feed themselves, and many perished of hunger.” Page 223: “Formica sanguinea, on the other hand, possesses much fewer slaves, and in the early part of the summer extremely few.” ↩
5. 30e.
  Page 223: “By what steps the instinct of F. sanguinea originated I will not pretend to conjecture.” ↩
6. 30f.
  Page 223: “it is possible that pupæ originally stored as food might become developed; and the ants thus unintentionally reared would then follow their proper instincts, and do what work they could.” ↩
7. 30g.
  Page 243: “it is far more satisfactory to look at such instincts as the young”. Page 244: “cuckoo ejecting its foster-brothers,—ants making slaves,—the larvæ of ichneumonidæ feeding within the live bodies of caterpillars,—not as specially endowed or created instincts, but as small consequences of one general law, leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live and the weakest die.” ↩
31.
Lanyon, Scott M. “Interspecific brood parasitism in blackbirds (Icterinae): a phylogenetic perspective.” Science 255(5040):77–79. Jan 3, 1992. Abstract only, from the PubMed record. Full text is paywalled and was not obtained. Copyright.
1. 31a.
  Section abstract: “Cladistic analysis of the sequence data indicates that brood parasitism evolved a single time within the Icterinae. The primitive form of interspecific brood parasitism in this assemblage is host-specificity, with host-generality representing the derived condition.” ↩
32.
Strohm, Erhard et al. “A cuckoo in wolves' clothing? Chemical mimicry in a specialized cuckoo wasp of the European beewolf (Hymenoptera, Chrysididae and Crabronidae).” Frontiers in Zoology 5:2. 2008. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 32a.
  Page 1: “The cuckoo wasp larva kills the beewolf larva and feeds on it and the bees.” ↩
2. 32b.
  Page 1: “The behavior to paper discs treated with a cuticular extract from H. rutilans females did not differ significantly from the behavior towards filter paper discs treated with the solvent only.” ↩
33.
Anderson, Michael G. et al. “Egg Eviction Imposes a Recoverable Cost of Virulence in Chicks of a Brood Parasite.” PLoS ONE 4(11):e7725. 2009. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 33a.
  Page 3: “cuckoo chicks in great reed warbler nests start to evict hosts eggs on average 2 days after hatching”. ↩
2. 33b.
  Page 1: “efforts to evict nest contents by the blind and naked common cuckoo Cuculus canorus hatchling”. “Here we show experimentally that egg tossing imposed a recoverable growth cost of mass gain in common cuckoo chicks during the nestling period”. ↩
34.
Gibbs, H. Lisle et al. “Genetic evidence for female host-specific races of the common cuckoo.” Nature 407(6801):183–186. Sep 14, 2000. Abstract only, from the PubMed record. Full text is paywalled and was not obtained. Copyright.
1. 34a.
  Section abstract: “We show that there is differentiation between gentes in maternally inherited mitochondrial DNA, but not in microsatellite loci of nuclear DNA.” ↩
35.
Fossøy, Frode et al. “Genetic differentiation among sympatric cuckoo host races: males matter.” Proceedings of the Royal Society B 278(1712):1639–1645. 2011. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 35a.
  Page 1639: “Our results imply that males also may contribute to the evolution and maintenance of the different races, and hence that the genes responsible for egg phenotype may be found on autosomal chromosomes rather than the female-specific W-chromosome as previously assumed.” ↩
36.
Hoover, Jeffrey P., and Scott K. Robinson. “Retaliatory mafia behavior by a parasitic cowbird favors host acceptance of parasitic eggs.” Proceedings of the National Academy of Sciences 104(11):4479–4483. 2007. The 56% and 6% figures are in the abstract. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 36a.
  Page 4479: “Here we present experimental evidence of mafia behavior in the brown-headed cowbird (Molothrus ater), a widely distributed North American brood parasite.” ↩
2. 36b.
  Page 4479: “No nests were destroyed when cowbird access was always denied or when access was denied after we removed cowbird eggs, indicating that cowbirds were responsible.” ↩
37.
Spottiswoode, Claire N., and Martin Stevens. “How to evade a coevolving brood parasite: egg discrimination versus egg variability as host defences.” Proceedings of the Royal Society B 278(1724):3566–3573. 2011. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 37a.
  Page 3570: “Of 125 rejection trials in tawny-flanked prinias, 63 eggs were rejected and 62 accepted. Of 59 trials in red-faced cisticolas, 26 eggs were accepted and 33 rejected. Of 37 trials in rattling cisticolas, 14 eggs were accepted and 23 rejected.” ↩
38.
Zimmermann, Holger et al. “Individual experience as a key to success for the cuckoo catfish brood parasitism.” Nature Communications 13:1723. 2022. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 38a.
  Page 3: “Overall, naïve catfish parasitised only 13% host clutches, while experienced and highly experienced catfish parasitised 25% and 29% host clutches, respectively.” ↩
39.
Sato, Nozomu J. et al. “Evicting cuckoo nestlings from the nest: a new anti-parasitism behaviour.” Biology Letters 6(1):67–69. 2010. Published online 23 September 2009. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 39a.
  Page 67: “The hosts forcibly pulled resisting nestlings out of their nests and dumped them.” “the studied host seems to lack an anti-parasitism strategy at the egg stage”. ↩
40.
Krüger, Oliver. “Brood parasitism selects for no defence in a cuckoo host.” Proceedings of the Royal Society B 278(1719):2777–2783. 2011. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 40a.
  Page 2777: “The cuckoo has evolved massive eggs (double the size of bulbul eggs) with thick shells, making it very hard or impossible for the host to eject the cuckoo egg.” ↩
2. 40b.
  Page 2777: “Non-mimetic eggs and absence of defence strategies against cuckoo eggs will be the stable, if at first sight paradoxical, result.” ↩
41.
Cash, Elizabeth I. et al. “Reference genome of the kidnapper ant, Polyergus mexicanus.” Journal of Heredity 116(3):293–302. 2025. Reports a genome assembly, not a study of which genes are missing. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 41a.
  Page 299: “these species have lost the ability to perform most typical worker ant behaviors, including foraging, nest excavation, and brood care”. ↩
42.
Foitzik, Susanne et al. “Coevolution in host–parasite systems: behavioural strategies of slave-making ants and their hosts.” Proceedings of the Royal Society B 268(1472):1139–1146. 2001. The paper calls the slave-maker Protomognathus americanus, now Temnothorax americanus. The abstract reports that raiders and defenders from the heavily raided New York population were both more effective than those from West Virginia. Publisher PDF from PubMed Central. Copyright. Mirror: PMC
1. 42a.
  Page 1139: “These raids decimate reproduction and growth in multiple host colonies in a single year”. ↩
43.
Achenbach, Alexandra, and Susanne Foitzik. “First evidence for slave rebellion: enslaved ant workers systematically kill the brood of their social parasite Protomognathus americanus.” Evolution 63(4):1068–1075. 2009. Abstract only, from the PubMed record. Full text is paywalled and was not obtained. Copyright.
1. 43a.
  Section abstract: “here we demonstrate the rebellion of enslaved Temnothorax workers, which kill two-thirds of the female pupae of the slave-making ant Protomognathus americanus”. ↩
44.
Schrader, Lukas et al. “Relaxed selection underlies genome erosion in socially parasitic ant species.” Nature Communications 12:2918. 2021. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 44a.
  Page 1: “The social parasite genomes show distinct signatures of erosion compared to the host lineages, as a consequence of relaxed selective constraints on traits associated with cooperative ant colony life”. ↩
2. 44b.
  Page 5: “we identified 32 fewer genes containing the characteristic 7tm6 domain of ORs than in its host A. echinatior”. “only 263 OR genes remained compared to 467 OR genes in the host A. heyeri”. ↩
3. 44c.
  Page 9: “In contrast to ORs, we did not find convergent reductions in GRs, CPRs, MRJPs, and elongases”. ↩
45.
Feldmeyer, Barbara et al. “Species-specific genes under selection characterize the co-evolution of slavemaker and host lifestyles.” BMC Evolutionary Biology 17:237. 2017. Selection is inferred from sequence comparison. Publisher PDF from PubMed Central. CC BY. Mirror: PMC
1. 45a.
  Page 1: “We identified 309 genes with signs of positive selection on branches leading to slavemakers and 161 leading to hosts.” “There was little overlap of genes with signatures of positive selection among species”. ↩
46.
Osipova, Ekaterina et al. “Comparative population genomics reveals convergent adaptation across independent origins of avian obligate brood parasitism.” Nature Ecology & Evolution 10(1):128–139. Jan 2026. Published online 12 December 2025. Abstract only, from the PubMed record. Full text is paywalled and was not obtained, so "no loss reported" means none is reported in the abstract. Copyright.
1. 46a.
  Section abstract: “we find evidence for adaptation in genes involved in sperm function in multiple parasitic clades, but not in the matched, non-parasitic outgroups”. “We also detect selective sweeps near genes associated with nervous system development in parasitic lineages”. ↩
47.
Carroll, Rachel A. et al. “Genomic resources for comparative analyses of obligate avian brood parasitism.” bioRxiv. Aug 15, 2025. Preprint, not peer reviewed. CC BY. Mirror: PMC
1. 47a.
  Page 3, section abstract: “little is known about the genetic basis of the complex suite of traits associated with this rare life history strategy”. ↩