Question: Are Tree Sparrows facultative migrants?

American Tree Sparrow: Strictly a winter bird in Ohio, leaving in spring to go far to the north.  How much is its departure time affected by local weather?  Photo by Kenn Kaufman.

Late March: Today I'm thinking about birds I'm not seeing.  For the last couple of years, I've seen small flocks of American Tree Sparrows around Oak Harbor throughout the winter and into spring, at least into early April.  There were plenty of them around this winter, but most of them seem to have disappeared in early March, about the time we started having record-warm temperatures.  Was their departure partly a result of the weather?

Researchers who study migration talk about different bird populations being obligate migrants -- those that move at a certain time of year, regardless of what the weather is doing -- and facultative migrants, which can vary the time of their migration (and even the distance that they migrate) depending on the conditions of the moment.  These are not two completely distinct groups, but rather two ends of a spectrum.  Most facultative migrants only vary their migration within certain limits -- that is, they won't suddenly start to migrate south if there's a cold day in June; the conditions have to fall within the right general time of year.

The most obvious examples of facultative migrants around here are various waterbirds, especially ducks, in their fall migration.  Many of them will come south to northern Ohio in fall and then linger as long as there is enough open water.  If it's a mild winter, they may stay the entire season.  Sandhill Cranes respond to weather also, so recently they've been migrating south later and later in fall, and staying through the winter farther north than they used to.

My question of the moment involves American Tree Sparrows.  Their breeding range is far to the north of here, in arctic and subarctic Canada and Alaska.  In a typical year, most will be gone from northern Ohio by mid-April, and almost all of them by the beginning of May.  This year, with record high temperatures for days at a time in March, the Tree Sparrows seem to have disappeared a month earlier than usual.  Did they, in fact, start north so much earlier?  I will be interested to find out if areas north of the wintering range had earlier spring records than usual.

Insight: Pumped-up Red-wings

A male Red-winged Blackbird. Yes, it is walking around looking for food in the dry grass on the roadside; and yes, it is pausing every few steps to sing. Photo by Kenn Kaufman.

Early March: Okay, I know this isn't directly related to migration, which is the focus of this effort.  But I can't help but notice the behavior of the male Red-winged Blackbirds that have set up breeding territories in the local marshes.

Some flocks of Red-wings are around all winter, but there's a point in February when a change in behavior is obvious.  Individual males spread out into the frozen marshes, to perch at the tops of the dead stems of last year's grasses, each one singing to announce his own claim to his breeding territory for the season.  The females may not have arrived in the area yet, the actual nesting season may still be weeks away, but those males are making sure they have staked out their turf. 

By now, in early March, the male Red-winged Blackbirds are really worked up.  I was just watching them along the road at Magee Marsh.  They will temporarily abandon their territories out in the marsh and will come to the short grass along the roadside to hunt for food.  But even there, while they forage, they will pause every few moments, puff out their shoulders, and sing.  I guess the instinct is so strong at this time of year that they just can't help themselves.

Question: Are some Killdeers migrating in pairs?

Killdeer in flight: is it flying solo, or with a friend? Photo by Kenn Kaufman.

Early March: Killdeers just started showing up in the area a few days ago.  I've seen them at about a dozen spots.  The thing that strikes me about them is that all the Killdeers I've seen have been in pairs.  So the question is: do they go through their courtship and form pairs very rapidly after they get here, or are they actually pairing up somewhere to the south of here, and arriving together? 

Killdeers don't leave northwest Ohio for very long.  Usually a few linger locally until mid-December, and the first returning birds are back by mid to late February.  They're common in winter just a few hundred miles to the south.  It would be plausible for them to form pairs on the wintering grounds.  The Birds of North America account for Killdeer doesn't shed any light on this.  It does say that Killdeers in the South may remain in pairs all year, and that those in the north may have the same mate for several years in a row. 

I guess I'll have to watch the arriving Killdeers more closely next year, to see if there's active chasing and courting on the day they arrive, or if the birds come in looking like established couples already.  But I'd be interested to hear from anyone who has more insight into this question.

Insight: Too much of a good wind

March 7: Here along the Lake Erie shoreline in n.w. Ohio, we get good hawk flights in spring mainly on days with southwest winds.  With any kind of south winds, or with warm calm weather with good thermals, the hawks will be moving on a broad front, but they won't concentrate anywhere.  Southwest winds push the birds up toward the lake shore, and they then correct and move west-northwest paralleling the shore, aiming for the west end of the lake where they can turn and go north into Michigan.

Today we had southwest winds but they were evidently too strong for a lot of the migrants.  With winds of 30 mph, and stronger gusts, there were probably no thermals rising anywhere, and the smaller hawks that were flying seemed to be having a tough time of it.  I spent a while at midday watching from the observation platform at the corner of Krause and Stange Roads (west side of Ottawa NWR) and saw very little flying.  (Well -- lots of debris, leaves, etc., flying on the breeze, but not many birds.)  Continuing west to Maumee Bay State Park, I counted 220 Turkey Vultures in an hour and a half, but only small numbers of other hawks (just a few Red-shouldered and Red-tailed hawks, Northern Harriers, and a couple of American Kestrels).  Even the Turkey Vultures were rocking in the wind, and the other birds were having a tough time.  I'm inclined to think that ideal conditions would have lighter winds, perhaps 15 to 20 mph from the southwest.