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Index of Subjects Hi, Peter. I've been away atlassing, so am just reading this series of messages now. I'd like to add that Ruby-throated Hummingbirds do typically raise more than one brood per season across most of their breeding range, so that seems the most obvious reason for males to remain. The Birder's Handbook (an excellent resource) indicates that this species has 2 and occasionally 3 broods. Being at the northern extreme of their range, we seldom see this here. But I helped document a successful 2nd brood raised by a female Ruby-throated a few years ago at Folly Lake (in NS, near the NB border). She was seen building the 2nd nest while still feeding the young in the first. Two young fledged from each nest. I understand that this was the first documented 2nd brood for NS, as far as reports to the Nest Records database go. A female hummer had built a late (July) nest in the same tree the previous year, presumably also a second nesting attempt, but had abandoned it before it was complete. This may be more common than we realize. Even with few second broods raised here, it seems to me advantageous for males to remain in the vicinity, in case of early nest failures, e.g. in cold, windy, rainy Junes. Cheers, Susann ----- Original Message ----- From: "Peter Payzant" <pce@accesswave.ca> To: <naturens@chebucto.ns.ca> Sent: Monday, June 25, 2007 1:18 PM Subject: [NatureNS] Re: Why do male hummers... > Hi, Angus et al- > > Yes, I'm aware that the males do leave earlier than the females. My > thoughts were more along the lines of "Why are there still any males > around now, at the end of June?" The females presumably are now all mated, > and the males don't help in nestbuilding or care of the young. > > I like Andrew's conjecture that there is little cost to the species in > having the males linger, and that they use the same cuing system (i.e. day > length) to tell them when to hit the road. If there was any advantage to > leaving earlier, they would of course be doing it. An alternative cue for > that might be several weeks of little change in day length, but that might > run a risk of them leaving too soon. It's a lot easier to detect a change > than it is to detect a steady state. > > Peter
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