May 24th – It’s All About Timing

Male Canada Warbler

The Spring migration is a frenetic rush to get to the breeding grounds and get ‘er done. There’s no time for sightseeing. Today the Killdeer eggs hatched and there’s 4 young, very “cute” chicks running around under the watchful and very nervous eyes of their parents. And they should be nervous – the chances of the chicks making it through the next few days, let alone the next year, are slim. Predators abound and are ever watchful. We can be a big problem in this regard. Potential predators are watching us although most of the time we’re not aware of them. But they are. When we go to get “a closer look at the cute little Killdeer”, the parents put up a fuss which draws predators’ attention and the little ones scurry about in a panic making them visible. The predators will just bide their time – they now know where the food is. The best thing is to try to observe from a distance with binoculars or a telephoto lens.

While the drama of the hatching Killdeer is unfolding, we’ve been catching SY (Second Year) Indigo Buntings, Rose-breasted Grosbeaks and Yellow Warblers (all long-distance migrants) that aren’t carrying any fat, indicating that they’re “local” birds; i.e., staying in the immediate area to breed. They’ve either just arrived or have arrived just recently and are moving around looking for a territory or breeding opportunity, as most of the territories have already been taken by older birds and are being fiercely defended. Some of these birds, sometimes know as “floaters”, will get lucky and find a niche; others may have to wait for next year. Either way, in the local Indigo Bunting, Grosbeak and Warbler communities, nesting is just beginning.

And then there’s the Blackpoll Warblers and Gray-cheeked Thrushes. We’ve just started to see these in the past couple of days – they’re typically late arrivers; probably because they’ve come such a long way, from wintering grounds in the jungles of South America. These birds still have a long way to go – the boreal forests of northern Ontario at least; the thrushes may head north and further west. Gray-cheeks breed as far west as Alaska. (There’s some evidence that these far northwestern-breeding birds, in the Fall, fly east or southeast to Ontario, before then heading south – an amazing feat of navigation as well as physical achievement. I’d love to know where some of the Gray-cheeks we catch in the Fall have come from.) These birds will not even start to nest until most of “our” birds here in southern Ontario are feeding young.

From their perspective, there’s not much time – a window of opportunity that must be seized. And the farther north a bird goes, the smaller the window is. But the benefits of fewer predators and an abundance of insect food (ah, blackflies and mosquitoes and spruce budworm catepillars) makes it all worthwhile.

For us here at Ruthven, then, the migration is drawing down. The bulk of the birds have moved through. We’ll continue monitoring until the end of May but get diminishing returns on our efforts. As well, we don’t want to impede the breeding efforts of our local birds (most of whom have learned where our nets are by now and are avoiding them). But it won’t be long until this huge biomass begins to move south again.

Male Yellow Warbler - G. MacLellan

Consider the Yellow Warblers that breed here in large numbers. They’re pairing up and building nests now. Very soon (and some maybe even now) they will start to lay eggs. A typical clutch consists of 4-5 eggs and they lay one a day. The female broods the eggs for 8-9 days and, once they hatch, the parents will continue to attend/feed them for another 2 weeks. Thus, in 3-4 weeks after hatching, the young will be independent of their parents. At that time the fledged young will begin to disperse and check out the areas surrounding the natal site with the possibility of familiarizing themselves with the area for their return next year – looking for good potential breeding sites. But they will soon start to move south. The parents on the other hand will start a complete moult, replacing all their feathers. This will take several weeks and then they too will start to head south. Do the math: if the early arriving females start sitting on eggs today, they will have independent young by the end of June. Some of these birds will start to head south and others, that spend some time investigating the immediate area, will start heading south in early July. The parents will start south around the middle to end of July. For them the Summer is over!

Banded 23:
1 Traill’s Flycatcher
7 Gray Catbirds
6 Yellow Warblers
1 Magnolia Warbler
1 Northern Waterthrush
1 Common Yellowthroat
1 Wilson’s Warbler
1 Canada Warbler
2 Indigo Buntings
2 American Goldfinches

Retrapped 24:
1 Blue-gray Gnatcatcher
2 Gray Catbirds
1 Red-eyed Vireo
1 Blue-winged Warbler
1 Nashville Warbler
4 Yellow Warblers
3 Common Yellowthroats
1 Rose-breasted Grosbeak
2 Chipping Sparrows
1 Song Sparrow
4 Brown-headed Cowbirds
2 Orchard Orioles
1 Baltimore Oriole

ET’s: 62 spp.

Photo Gallery (thanks to Gail MacLellan):

Male Rose-breasted Grosbeak - looking for a finger to bite. - G. MacLellan

Gray Catbird - G. MacLellan

Male American Goldfinch - G. MacLellan

Beautiful ASY male "Baltimore" Oriole - G. MacLellan

Male Common Yellowthroat - G. MacLellan


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