Migration

As a long time bander I will chip in on this. For North American birds, I am most familiar with neotropical migrants on the west coast having worked and worked the data at several MAPS (MONITORING AVIAN PRODUCTIVITY AND SURVIVORSHIP PROGRAM) stations in the Sierra Nevada in the 90's. The original intent of the program was to figure out individual survivorship of migratory birds because no really good data existed for individuals and there was (and there remains) great concern about declining populations of migratory bird habitat on the winter (non-breeding) range. Of course, that is the case (as we sip our Central American coffee), but other patterns emerged over time, some of it well documented by banding records and some speculative and intuitive after nearly 20 years of collecting data (the program began in 1989). In short, lots of different things happen.

One relatively common thing that happens is that birds that winter in temperate places like the Willamette Valley, the Sierra foothills, or Baja California often breed very far north but are replaced by birds that winter further south but arrive as the northern breeders depart. I watched this with Pacific-slope Flycatchers working on the Channel Islands but only in retrospect - the wintering flycatchers would "disapper" for a few days and then suddenly you would start hearing them again, not the same birds but the cousins in from Costa Rica ... I suspect that breeding Varied Thrushes in Oregon are not the birds we see in the Coast Range in January, after all their old name was "Alaska Robin", but instead birds that spent December and January in Big Sur. You also see this statistically as recapture rates change - as the breeding season progresses recaptures of birds banded in prior seasons increases. Some birds are altitudinal migrants for breeding, often following the snow line upslope on exploratory forays but there is also the phenomenon of birds breeding very early and young dispersing upslope from their hatching area and breeding again (as young of the year) at a higher altitude. Orange-crowned Warblers do this in the central Sierra and suspect Juncos often do the same. Another interesting phenomenon that I have observed from banding on wintering ranges is altitudinal segregation of populations on the wintering range. You see birds like Hermit Thrushes with distinctive subspecies or populations that can be identified in the hand segregating by altitude - high latitude breeders at higher altitudes on the winter range and lower latitude breeders at lower altitudes.

All this is made possible by the somewhat arcane (and often more art than science) of ageing birds by feather wear, subtle plummage variations, skull suture patterns, breeding condition (brood patch age, cloacal protuberance) and of course simple recapture data (see Identification Guide to North American Birds Part I by Peter Pyle). At one MAPS location near Yuba Pass in California there was a Yellow Warbler that was captured for 9 consecutive seasons in the same willow with the first recapture always within a few days of the prior years' capture. He was certainly not the champion. I moved to Southern Africa and did similar work there for many years (coming back to the States a few years ago and landing in Oregon) and the fascinating thing is that paleotropical migrants are much longer lived than our neotropical migrants - a nine year old passerine banded in temperate South Africa is relatively ordinary and there is no reasonable explanation as to why ... yet. Any prospective grad students out there looking for a project?

Best regards,

Mike Gellerman

From: David Fix & Jude Power <foglark@att.net>
To: obol@oregonbirdwatch.org
Date: Tue, 14 Apr 2009 12:28:47 -0700 (PDT)
Subject: [obol] spring departure of wintering birds
In recent OBOL posts, there has been discussion about where wintering Dark-eyed Juncos, Varied Thrushes, and similar species usually seen only in winter in the lowlands at many locations go when nesting season arrives.

Some have suggested that juncos, to name one example, move upslope into the mountains to nest. While this is likely the case for many, it seems to me that it is a bit short-sighted. To inject a dissenting point of view, I suspect that a huge number of wintering juncos (I would imagine many tens of thousands) don't move upslope, but instead leave Oregon entirely, and may fly hundreds of miles, into Washington and way up into British Columbia. Conversely, it may be that many of the juncos that breed in the foothills and mountains of w. Oregon don't even winter in the state, but do so farther south. Perhaps Dennis Vroman or some other bander might chip in on this.

The same could be true for Varied Thrush, whose breeding populations north of Oregon (based on range, and amount of habitat) are likely far greater than those within the state.

Similarly, when we see birds such as Orange-crowned and Wilson's Warblers and Pacific-slope Flycatchers "arrive," it seems likely--if based merely on the immense populations of those species, and their vast ranges--that nearly ALL of the individuals we encounter are not going to breed locally, and perhaps most not even in Oregon; they could well be headed toward the more northerly part of their range. Many of the Orange-crowns seen in an April morning on Skinner Butte in Eugene could well be in Chehalis, Bremerton, or coastal B.C. a few days later.

It's easy to think of these as "our" birds, about to settle in for the summer, but a look at the range maps for many will suggest that maybe that's not the case. The truth is not available, but I thought I'd suggest an alternate scenario.

David Fix
Arcata, California

Planted onions and potatoes today, quatre saison lettuce, spinach and mesculun look good. Garlic didn't come in as well as usual so maybe we can plant some more. The artichoke is ready to go and we think there is a zuchini coming up.

I was putting the canoe out in the backyard and moving around some old wood when I found this creature. We have never seen so much as a newt around Bethany Pond, but when we looked him up he is the Western Long-toed Salamander (Abystoma macrodactylum) and happens to be the second most common

Lost at Scrable Again

This makes two in a row. It all seemed to be going so well and she was even sleepy. Stay tuned for a rematch