Monday, August 11, 2008

Timing of shorebird migration

Shorebird migration seems to be proceeding at a normal pace in northwestern Ohio, in terms of both numbers and timing. Areas of shorebird habitat have been changing constantly over the last six weeks ... as is also normal. Stopover habitats for shorebirds are changeable by their very nature -- changing by the hour in tidal situations at the coast, changing by the day inland, as low-lying areas flood or dry up. The shorebirds, ever adaptable, are quick to take advantage of new habitat, quick to move on when it loses its appeal. Most migratory shorebirds are such strong fliers that they can keep going for hundreds of miles, at least, until they happen to find a good spot. In an inland region like Ohio, when an area of good habitat appears, shorebirds migrating over will drop in. So these temporary habitats give us a chance to take a sample of what is passing overhead.

I had a chance to sample what was pausing in the back country of Ottawa National Wildlife Refuge on Friday, Aug. 8, and today, Monday, Aug. 11, when I tagged along with a team doing research there. (Unfortunately, as reported earlier, the auto tour at Ottawa won't be open this weekend, owing to unforeseen delays in construction, but the main shorebird concentrations right now are away from the auto tour anyway.) These are my very rough numbers from one major impoundment from today, estimated when I wasn't up to my knees in glutinous mud:
Semipalmated Plover 20 (mostly adults)
Killdeer 35
Greater Yellowlegs 14 (mostly adults)
Lesser Yellowlegs 90 (more juveniles than adults)
Solitary Sandpiper 15 (those seen well were adults)
Spotted Sandpiper 10 (adults and juvs)
Semipalmated Sandpiper 120 (roughly equal numbers of adults and juvs)
Least Sandpiper 200 (more juvs than adults)
Pectoral Sandpiper 40 (adults)
Stilt Sandpiper 2 (juvs)
Short-billed Dowitcher 25 (1 adult, the rest juvs)
Wilson's Snipe 4
The mix on Friday 8/8 was similar, but with the addition of one Long-billed Dowitcher and two Dunlin, and larger numbers of Short-billed Dowitchers. Also on Friday, slightly fewer of the Semi and Least Sandpipers were juveniles.

I'm not mentioning these birds to frustrate birders who can't get into closed areas of the refuge, but just to indicate that there are indeed good numbers migrating through. Fortunately, I didn't see anything rare on the refuge, and all of these species could be expected in visits to the Bellevue ponds and other accessible sites.

The timing of dowitcher migration is worthy of special mention. Hundreds of Short-billed Dowitchers were passing through the area a month ago; for example, I counted 86 on one impoundment at Pickerel Creek on July 4, and others had higher counts there. Western Ottawa County had very heavy rains in early July, causing damage to some local crops but creating temporary shorebird habitat, and many dowitchers (all adult Short-billeds of the prairie race, hendersoni) paused in these flooded fields. On July 10 I saw a dozen in a flooded front yard in the town of Rocky Ridge! July is the peak migration season for adult Short-billeds here; by now the great majority of the adults have departed, and numbers of juveniles have not yet reached their peak. Meanwhile, a few adult Long-billed Dowitchers can be expected now, but juveniles aren't likely to show up until September.

Many areas of shorebird habitat near the lakeshore are far more accessible to the birds than to the birders. For good viewing, for the time being, it's probably best to keep checking the flooded fields near Bellevue. One particularly good spot recently has been on TR 292 just north of the Sandusky/Seneca County line; a few days ago, these ponds still had four Black-necked Stilts and three Wilson's Phalaropes.

Mid-August is a great time to be looking at shorebirds. The differences between adults and juveniles are very obvious for many species now, and the juveniles are particularly beautiful in their crisp new plumage. Paying attention to the ages of shorebirds in fall will really pay off in increased understanding of the timing of their migrations. For most species, the adults migrate south before the juveniles, and keeping this in mind will help you to make sense out of what you're seeing.

1 comment:

Anonymous said...

Could you fill us in on what you mean by "Bellevue"? It isn't on your "Birding Hotspots" page, and a Google search didn't turn up anything useful either.

Ted Miller, Elkhart, IN

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