When last I wrote on this topic, the pair of Cordilleran Flycatchers nesting on a beam over my front porch and under the roof had removed 3 of 4 eggs from the nest (placing them in the corner between the nest and rafters) and one young had been hatched.
Theories for the egg-removal behavior centered around the following four ideas: a. Parents detected infertile eggs and removed them (e.g. lack of movement and/or heat from egg) b. New male removed eggs in support of his own. This would have carried more momentum as a theory if all eggs were removed and a new clutch were laid. Since the remaining egg that hatched was from the original clutch, this doesn't seem very probable in this situation. c. Removal of eggs to reduce clutch size and mouths to feed in times of scarcity. But, this season in Teller County certainly seems to be one of the most bountiful in many years. Flying insects of all sorts seem to be faring extremely well. d. Cowbird laid an egg, prompting somewhat erratic behavior of multiple egg removal. (e.g. Yellow Warblers may abandon currently laid clutch when a cowbird egg is detected and build new nest on top of old; then lay new clutch.) There are various other species-related responses to parasitic egg-laying, but I have yet to read of something similar to this. Yesterday, during high wind from one of many storms moving through, the nest blew down along with one of the stashed eggs. The nestling, in its ~12th day of life, remained on the beam along with the remaining two eggs. The egg that blew down was cracked and I inspected. There was a fairly well developed individual inside; pin feathers and skin and bill were noticed. Tonight at 7:30pm, while working on the computer my wife alerted me to much calling from the flycatchers. When I looked out our upstairs window where the nest had been for a month and the nestling for two weeks - nothing! "It has fledged Connie!". We looked outside to see it in the driveway. It soon quite adeptly flew up into a nearby tree! ~13 days from hatching. Now it is time to inspect the 2 remaining eggs: 1 had a completely formed bird inside while the other was mostly yolk with a slight blob-ish growth starting to form. This finding would seem to rule out theory "a" above as two of the three removed eggs seemed to be viable. As of this date, no one has contacted me, nor has any web research or otherwise turned up anything to shed light on this behavior of egg removal that seems to fit the variables. Chronology of events: 6/14 - find nest started 6/20 - first egg seen this morning; eggs laid every other day at mid-day. 6/24 - female started incubation; the previous day there were only 3 eggs. Assumed that 4th egg was laid. 7/7 - nest had one egg removed. 7/10 - 3 eggs removed from nest and 1 nestling hatched. 7/23 - single nestling fledged. If anyone finds any information on such egg-removal behavior among any birds, I would love to hear about it. I hope they come back next year! J 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 -~----------~----~----~----~------~----~------~--~---
