Sounds about right. I'd have to check the BNA account tomorrow at work to verify the numbers, but that seems in the ballpark.
For medium-sized songbirds, like robins and Red-winged Blackbirds, 70% of nests fail to produce any fledglings, 92% of those fledglings die over the first year, and half of all adults die each year. Larger birds tend to have higher yearly survival, but they take longer to reach maturity, too. For American Crows, roughly just over half of the nests produce fledglings, half of those survive their first year, but most don't breed until they're 4 years old, and it's 15% mortality each year. Bald Eagles don't breed until they're 5 or so, so I would expect numbers something Pete quotes. It's a rough world out there. That's one of the reasons that natural selection is so strong at weeding out "frivolous" behavior. Kevin ________________________________ From: bounce-120838092-3493...@list.cornell.edu <bounce-120838092-3493...@list.cornell.edu> on behalf of Peter <psara...@rochester.rr.com> Sent: Wednesday, September 28, 2016 7:23:58 PM To: CAYUGABIRDS-L; CAYUGABIRDS-L Subject: [cayugabirds-l] Eagle Question Howdy folks. Am reading a very interesting, creative book by Pete Dunne called "The Wind Masters....The Lives Of North American Birds of Prey". Dunne takes a very creative approach to teach us about these birds...the book reads more like a novel! I highly recommend it but have a question. In his piece about Bald Eagles, Pete says that, with respect to young eagles, more than 90% that fledge in a given season don't survive to adulthood, and nearly 60% of these die during their first year. Evidently, to quote Dunne, "starvation is a young eagle's greatest adversary".. I was wondering what anyone thought about his statistics..... Thanks for the feedback. Pete Saracino -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES http://www.NortheastBirding.com/CayugabirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/Cayugabirds 3) http://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBird: http://ebird.org/content/ebird/ -- -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES http://www.NortheastBirding.com/CayugabirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/Cayugabirds 3) http://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
