Bird behavior: A hatchling’s survival is anything but guaranteed
By the Masked Biologist
Special to the Star Journal
Recently there has been a lot posted in the media about leaving baby animals alone, even if you think they are abandoned, because they may actually be waiting for their mother to return, and your activity could interfere. Birds are a very good example of this behavior. In most cases, if you see a fully feathered baby bird, on the ground or a low tree branch, it is probably there because its mother lured it out of the nest, and is going to bring it food eventually.
Now, let me be clear on something. If you pick up a baby bird and put it back in its nest, its mother will not abandon it. Human scent on a baby bird does not result in being orphaned. I have to make that clear right off, because your mom probably told you that, just like my mom told me. Sorry, mom.
It is possible, though, that a baby bird on the ground was pushed out of the nest by another occupant, and if you put it back in, it may just get pushed back out again. I can’t help but wonder if this were the origin of the old wives’ tale. If the bird is not healthy or fit, a parent or sibling eliminating it is basically survival of the fittest. One less mouth to feed puts a lot less stress on the parents, and means more food for the stronger hatchlings, especially in years when food is scarce. There are other reasons a bird could get ejected from a nest, though. It could be blown out by wind, grabbed and dropped by a predator, or the nest could be knocked down.
Another possible explanation for a fledgling being ejected from a nest could be due to nest parasitism.
Some bird species, like cowbirds, reproduce strictly by laying eggs in the nests of other bird species. The cowbird egg hatches sooner than the eggs that occupy the nest legitimately, and instinctively pushes the other eggs and babies out of the nest. Bad baby! The result – parents lose their entire nest, and feed and care for the evil baby of another species. Some bird species, like American robins, blue jays, and brown thrashers reject the eggs, or even the nest. Other species, like vireos, song sparrows, and warblers, readily accept and hatch the eggs. In fact, there are some bird species that are seeing declines in reproduction and overall population numbers as a result of this cowbird nest parasitism. Some other bird species “dump nest” which is sort of like parasitism on your own species.
Wood ducks are great at this—a hen will crawl into an unattended nest of another wood duck hen, lay an egg, and take off. I have seen wood duck boxes where over 20 eggs were dumped in one box! From what I could tell, the resident hen eventually found something was wrong, and she abandoned the nest. Interestingly, although yellow-billed cuckoos usually nest, they will sometimes lay their eggs in other birds’ nests—either other cuckoos, or robins, wood thrushes, or grey catbirds. Apparently they only do this when some kind of insect outbreak results in an abundance of food for their young.
Some chick swapping happens after hatching in the bird world as well. Canada geese sometimes pick up the young of other broods, expanding their own little troupe. Hen turkeys will sometimes join forces, forming “gang broods” that may have three or four hens and a couple dozen chicks, or poults. This helps increase survival of individual chicks and lets populations expand rapidly.
By the numbers, survival of birds from egg to adult is frankly, very low. The death of young hatchlings is common and natural. Still, our instinct as humans is to help injured or orphaned wildlife, even if we are not sure how. Our good intentions can do great harm, though. If you see a young bird that you think needs attention, before touching a baby animal, contact your local wildlife rehabilitator and they will know what to do.
The Masked Biologist earned a Bachelor of Science degree from a university with a highly regarded wildlife biology program. His work in natural resource agencies across the country provided opportunities to gain experience with a variety of common and rare fish, plant and wildlife species. Follow The Masked Biologist on Facebook. Email questions to MaskedBiologist@charter.net.