[CT Birds] bobolink stuff (by popular demand)
ghanisek at rep-am.com
Wed Sep 8 16:44:40 EDT 2010
Since the report of 2300 Bobolinks at Lighthouse Point on Monday I've gotten a number of e-mails with a variety questions about what's going on. So here's a Bobolink primer for southbound migration:
First of all, I think most people are familar with Bobolinks when the males are singing on territory, often in the air, in hay or fallow fields, and the females are staying mostly hidden amid the vegetation. A number of people on this list have been involved in efforts to get the owners of such fields to use a mowing schedule conducive to the Bobolinks breeding successfully. Once the breeding season is over Bobolinks don't stick around long. They're early southbound migrants, not surprising considering how far south into South America they travel. Birds of North America Online says: "Makes round-trip, transequatorial migration of ca. 20,000 km between breeding and wintering grounds-one of longest annual migrations of any New World passerine." They're a signature species during the early stages of each fall's Lighthouse Point Hawk Watch, which is sponsored by the New Haven Bird Club. They are seen flying by, and there's no place else in the state I know of where you can consistently observe major flights. I don't ever recall seeing one on the ground at Ligthouse during fall migration. How early can you see migrant Bobolinks flying over Lighthouse Point? Over the years I've tried to get down there on cold fronts during July to see what's going on. My notes indicate I logged 50+ in a couple of hours on the morning of July 20, 1999. Many of these were molting adult males, showing blotchy black underparts. More on plunmage a bit later. The peak is probably the last 10 days of Aug and the first 10 days of Sept.
How unusual is a flight of 2300 Bobolinks? It's the largest number I've recorded, but it also appears to be in the typical range for a peak flight day. And the date is also typical. This fight was on Sept. 6. I also recorded 2100 on Sept. 7, 1998; 1800 on Sept. 9, 1995; and 1100 on Sept. 4, 2000. The latest I've noted one at Lighthouse is a single bird on Oct. 31, 1994.
How do you count that many birds flying by? A number of people who visit Lighthouse regularly in the fall have been practicing counting flock sizes for a number of years, primarily by sectioning off big flocks into manageable units. A real key is finding the birds in the sky, especially in a cloudless sky such as we had Monday morning. Fortunately Bobolinks are noisy, announcing their approach with flight calls. On Monday there were 5 of us who were all fully engaged (in the absence of hawks) in finding and counting the flocks. We regularly bounced numbers off of each other, and I record numbers flock by flock. Only later when we add these up do we really know how many we've seen. And of course we're never deluded into thinking we've seen them all.
The other question I've gotten is: How do you identify them? Their flight calls are unmistakable once you'ver learned them. It's a "bink" or "pink" with a certain amount of richness to it. When you hear it, start searching the sky for a flock of birds, pretty similar to a flock of waxwings. One thing we've all noticed is that the amount of sound you hear doesn't always correspond to the number of Bobolinks. Sometimes they seem pretty noisy, but you find only 2 or 3. Then what seems like the same amount of sound may turn up a flock of 100+. At this time of year, the Bobolinks are extremely uniform-looking. The males have all molted out of breeding plumage and many of the birds are juveniles. (Birds of NA Online says the flocks at this time are of mixed age and sex). They're essentially very yellow-looking birds, with the richness of color often accentuated by the low morning sun. They're also generally somewhat slimmer and longer-looking than waxwings, which are chunkier. The waxwing flocks also tend to bunch up more, but that's probably too subtle a difference to be a lot of help with ID.
Call notes are the key. A call note to eliminate while you're learning is Purple Finch. We've had a few already, but right now (although not for much longer) Bobolinks should be much more numerous. The Purple Finches have a "pik" call, often repeated a few times in quick succession. It's drier and sharper than the Bobolink, without the rich, slighthly more drawn-out "bink."
More information about the CTBirds