To follow-up on the egg-removal behavior of the cordilleran flycatchers nesting on my front porch. I have received many responses that fall into two main categories of explanation.
1. The pair recognizes when an egg should start producing heat and/or movement and in the absence of that, remove the aberrant eggs from the nest. This might seem to fit my case as each of the 3 eggs were removed one day apart. But, the intelligence required to recognize which egg was laid in which order and so on when many birds can't recognize a cowbird egg when it is in the nest, seems extraordinary. Or perhaps the egg-a-day removal was pure coincidence, and in no way is related to when each egg was laid. 2. A new male was introduced into the scenario which removed eggs forcing the female to be receptive and produce/lay more eggs fertilized by the new male. This behavior has apparently been recently reported on and a show produced for species such as Barn Swallows, Ringed Plover, etc. This behavior is exhibited in the animal kingdom elsewhere, for example, when adult male grizzlies kill cubs to force the female to be receptive and father his cubs. This theory has problems in my case as all 4 eggs were laid in sequence. Unless the new male was introduced between the 3rd and 4th egg; in which case, why wait until scheduled hatching to remove 3 eggs. I don't find either theory completely persuasive for the reasons stated above. Simple web searches don't find much support for either of these nor do they provider alternative theories that have yet to be postulated. I could put forth a theory about limited resources forcing the parents to reduce the number of young to care for. But this season is particularly rainy and producing many flying insects. So unless the rain is somehow limiting their favored food and producing lots of food they are unable to take advantage of, it doesn't seem likely. The lone hatchling in the nest is getting bigger, while the 3 unhatched eggs remain out of the nest in the corner of the rafters. Yesterday, I watched as the male brought food to the nest containing the brooding female (keeping the nestling warm) and the nestling; gave the food to the female, which in turn, fed the nestling while the male stood on the edge of the nest. fyi Jeff J Jones ( <mailto:[email protected]> [email protected]) Teller County - 8500' - Montane Woodlands --~--~---------~--~----~------------~-------~--~----~ Colorado County Birding: http://www.coloradocountybirding.com/ You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.as/group/cobirds?hl=en -~----------~----~----~----~------~----~------~--~---
