Sometimes nature must take care of itself. A mother egret out looking for food all afternoon came back to the nest only to throw one of the three chicks out of the nest. Without blinking an eye she continued to feed the other two. Nature knows best. The chick in the photo shows it being pulled under the water by turtles, I'm not sure if they were Ninja's or not.
This is fascinating Gary and you have made a very poignant image of the event. What you witnessed was almost certainly a case of "active" brood reduction. Passive brood reduction is the norm whereby in times of low food supply, the youngest or weakest chick in the brood is not able to compete for food with its siblings and eventually dies. Usually the chick lost is the last to hatch as this one is younger and smaller than the rest and not able to compete for food as well.
Active brood reduction where the parent or one of the chicks kills a chick or removes it from the nest is a much rarer observation, particularly when perpetrated by the parent itself. In certain groups of birds such as raptors, one chick- usually the smallest- gets "picked on" by its bigger siblings and may be actively killed. This tends to occur when food supplies are low. Black-legged Kittiwakes also commit "siblicide". In these cases the parents leave it to the "kids" to settle this. Now, this is not my field of biology, but I have never observed or heard of a parent actively reducing the brood as you witnessed. Anyone else has examples from other species?
Why this all goes on is to adjust the brood size to best match the available food resources in any one year, which is variable and often unpredictable. It is best from an evolutionary perspective to reduce brood size as quickly as possible so that resources are not wasted on the chick that eventually dies. If brood reduction did not occur you could have the possibility of all the chicks in the brood being malnourished in poor food years, possibly resulting in zero production of young that year.
By the way, it could equally have been the father egret that did the deed.
Last edited by John Chardine; 07-20-2009 at 06:46 AM.
Sad, but I agree with John that this is fascinating. I also have not witnessed or read of a parent bird actively reducing the brood size. Very interesting.
There's a fascinating example of this behavior on the BBC's Life of Birds, a must view for any birder. It's the footage showing (I believe it's) a Coot killing off it's own young. Gruesome, but fascinating!
Common Loon adults will attack one of their chicks until they drive it up on land where they usually die. A sibling will attack as well. I'm not saying the adult and sibling attack at the same time. My father watched an adult attack one of its chicks and never felt the same about loons again.
A rehabilitator friend of mine was the first person to ever raise a Common Loon chick that had been driven off. It had many wounds on its head when it arrived at the centre.