Darren wrote:Can you comment on the following:
1.) Do BW's move down in waves of some kind, sorted in some way? Early males that haven't stayed behind with broods? Other?
2.) When that mass is missed, as in 2017, are we basically SOL for the remainder of the 16 days? and
3.) These birds banded in Port Barre (in spring) opted to go to Texas coast in the subsequent fall migration. Is that common? Did they not imprint on Louisiana? Or is it just a crap shoot of which way they'll head each fall?
Thanks for kicking it around with us
1) Males have no role in brood rearing in most duck species. They "abandon" the hen once she gets into incubation, and goes on about his business of maybe finding another hen (one that lost her nest and has time/energy to renest), molting his wing feathers, and for bluewings, heading south. The first migrants are adult males, followed by females and juveniles.
2) I'm not sure. We almost always miss the first bunch of migrating bluewings that tend to move through in early September, but there is a steady, unpredictable stream in most years. I remember in the late-90's when I happened to be in North and South Dakota during mid to late-September for a string of years, and seeing the LA and TX internet forums light up with "they're here!" and tales of great early-season teal shooting. But all the while, I was seeing HUGE numbers of bluewings in every pothole in SD and ND.
I like to gauge the migration based on the age/sex composition of the harvest, acknowledging that I don't get to see a representative amount of it. On the opening 3-day weekend last year, we worked 2 "picking houses" for avian flu samples in SW LA, and the reports from my guys were that not only did they have about 1/3 of the normal number of birds, but nearly half were females.
Those are generalities. I have no idea how many we miss early vs how many migrate late. In some years a bunch of them stay (usually after a hurricane), and other years they don't. In the 14 years I've been flying the surveys, there seems to be more bluewings staying for the regular duck season compared to the past.
3) Bluewings are considered a "pioneer" species in the old waterfowl literature. They favor shallow-water habitats, which are highly dynamic, and they have the ability to find them when and where they become available. I think imprinting, especially to a winter site, means less to them than say a species like scaup, that exploit a food resource of more stable, predictable habitats.
I haven't followed up to know what a typical recovery distribution for those Port Barre birds looks like. If our season was open, we might have taken a lot more in LA than they did in TX. But remember those birds were banded on their spring migration, where ducks often use different habitats than in the fall.