can birds count their eggs

According to Bruce E., American coots (Fulica americana) secretly invade a neighboring nest to lay an egg for the other family to raise. This results in subtle egg wars between the families. Lyon of the University of California, Santa Cruz. His remarkably thorough research demonstrates that coots do indeed retaliate. According to Lyon in the April 3 Nature, they frequently count up the legitimate ones and relocate or destroy the dubious eggs.

Malte Andersson, a different egg sneaks researcher from the University of Göteborg in Sweden, is more receptive to the recent findings. According to him, numerous laboratory tests have indicated that captive animals are capable of counting, and this new study offers one of the earliest instances of animals counting in the wild.

Lyon compared the records of birds that eventually accepted parasitic eggs with those of birds that rejected them in order to determine whether coots can count. Receptive coots typically laid fewer eggs—roughly one less than each intruder egg. There were the same amount of parasitic eggs in the nests of both groups of birds at the crucial moment when their bodies decided whether to cease releasing eggs. Lyon contends that the accepting birds were duped by the fakes, and that both groups were counting how many eggs they thought were their own.

Before he agrees that coots count, parasitic bird expert Stephen Rothstein of the University of California, Santa Barbara, says he would prefer to see experiments that alter the birds’ perceptions as opposed to this study’s detached observations.

During four breeding seasons, Lyon and his enthusiastic field assistants observed coot nests in a marsh in British Columbia every day. Of the more than 400 nests, 41 percent had stealth egg layers. Half of the chicks perished from parasitism, and an intruder among the early hatchlings stole food that could have saved a later-emerging, legitimate resident.

Checking the nests daily, Lyon and his field assistants monitored the whereabouts of each egg in over 400 coot nests. Since a bird can only lay one egg per day, parasitism was easily found. Additionally, color and speckle pattern are frequently used to distinguish coot eggs laid by different parents.

Lyon discovered that female coots are highly skilled at identifying and shunning parasitic eggs. Nesting material buried the rejected eggs, preventing them from hatching. Sometimes, rather than being rejected outright, parasitic eggs were sent to less favorable incubation environments, which caused the parasitic chicks’ chances of survival to decrease and their hatching time to be prolonged.

Lyon’s initial goal was to investigate how coot parents raise their young. However, when he found incredibly high levels of “brood parasitism,” or the habit of laying eggs in other birds’ nests, his research’s focus shifted. The majority of research on brood parasitism has focused on birds like cuckoos, which deposit their eggs in the nests of other species to save themselves the trouble of raising their own young. However, brood parasitism can also exist within species, and Lyons’ coot research is providing fresh insight into this little-known phenomenon.

University of California, Santa Cruz SANTA CRUZ, CA — A new study demonstrates that common marsh birds, or coots, can identify and count their own eggs, even when there are eggs laid by other birds nearby. This finding may lead to coots being treated more respectfully, like the Rodney Dangerfields of the bird world.

If the birds are touch-cued, a female should lay fewer of her own eggs if there are parasitic eggs present. However, Lyon discovered that female coots did not decrease the size of their clutch when they realized there were parasitic eggs in their nests and eventually rejected them. On the other hand, females that were unable to identify parasitic eggs produced one fewer egg of their own for every parasitic egg they were given.


Can birds recognize their own eggs?

Brood parasitized and/or colonial birds use egg features as visual identity signals, which allow parents to recognize their own eggs and avoid paying fitness costs of misdirecting their care to others’ offspring. However, the mechanisms of egg recognition and discrimination are poorly understood.

Do birds sit on their eggs constantly?

In some species of which only a single parent incubates, its absences are far shorter than its sessions, so that a high constancy of in- cubation is achieved; in others, the absences are of about the same length as the sessions with which they alternate, so that the eggs are covered only about half of the day.

Do birds know if their eggs are not viable?

Yes. Birds will recognize and reject a dead egg.

What determines how many eggs a bird lays?

Females lay fewer eggs per clutch when breeding in colonies or other high population areas. Geographic location. On average, within a species, birds lay smaller clutches when breeding at either lower latitudes or higher altitudes.