The subject of Siblicide and aggression among nestlings often comes up when the bonking starts among nestmates in the Decorah nest, and some other nests we may follow. There is a thread in Forum (on the "Other Raptors Cams" board) for the Black Eagles of South Africa (also known as Therreaux's Eagles), and the first egg was laid today in that nest. When I mentioned it in another Forum thread today, another member cautioned people about watching that cam because siblicide is typical there and is an expected practice in that species, as well as parental aggression toward the fledgling to get it to leave the parental pair's territory. This can be difficult to watch.
Anyway, that led me to discover and post the following info about Avian Siblicide. There are two very different and distinct forms of avian siblicide - the type practiced by Black Eagles (and some other species of birds), which only lay two eggs, and almost always results in the death of the 2nd nestmate, and the other type that is related to environmental factors, which is the type sometimes (but not always) seen in some Bald Eagle nests, for example (and other species of birds), and is the type that can vary greatly even among a species. Due to the very favorable environmental factors, such as a steady, year-round, ample supply of food, and parenting behavior, we haven't seen this in Mom and Dad Decorah's nest, even though there is aggression between the nestmates, which hasn't resulted in death in the Decorah nest.
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Here's are some interesting things I have learned about avian siblicide...
The Verreaux's Eagles (Black Eagles) of South Africa usually only raise 1 chick per season. Siblicide is typical behavior in their nests if they hatch more than one egg. This is also true in some other species of birds. As described by Douglas W. Mock, Hugh Drummond and Christopher H. Stinson, in their publication, "
Avian Siblicide," "The black eagle is one of the first birds in which siblicide was described." Another thing I learned from this article is that
there are two very distinctly different forms of siblicide - one is known as obligate, and the other is known as facultative. Obligate siblicide is found in certain species that usually only ever lay two eggs and the first-hatched chick almost always kills the second one. This is the type of siblicide found in Black (Therreaux's) Eagles, and some other types of birds. The other type of siblicide, called facultative siblicide, is the kind that varies based on environmental factors (availability of food, etc.) - as can happen in some Bald Eagle nests (and other birds), and why we don't see it in Mom and Dad's Decorah nest, because of the abundance of food at that nest. And this type of aggression varies widely among different populations of the same species - more so in some, and not at all in others
That is a very informative article about Avian Siblicide, BUT...
**NOTE*** VIEWER ALERT*** There are photos of siblicide in that article, so you may choose not to look at that article *** That article can be viewed without downloading it, and can be found at
http://www.academia.edu/3826423/Avian_Siblicide(Douglas W. Mock is associate professor of zoology at the University of Oklahoma. He was educated at Cornell University and the University of Minnesota, where he received his Ph.D. in ecology and behavioral biology in 1976. Hugh Drummond is a researcher in animal behavior at the Universidad Nacional Autonoma de Mexico. He was educated at Bristol University, the University of Leeds and the University of Tennessee, where he received his Ph.D. in psychology in 1980. Christopher H. Stinson was educated at Swarthmore College, the College of William and Mary and the University of Washington, where he received his Ph.D. in 1982.)
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Topic: New developments in the field of science (Read 447290 times)