August 3rd – They’re on the Move

A wonderful Summer day, which started with a cool clear morning. There were a lot of birds around, mostly high in the trees busily foraging. In fact, I recorded 51 species (which didn’t include a Bald Eagle I saw over the river shortly after leaving Ruthven). The birds seemed to be in groups – mixed species flocks. Perhaps the best spot was down by the Thompson cemetery. (I have to confess that this is my favourite spot on the whole Ruthven property.) I spent half an hour between net rounds stretched out on the bench there just watching the tree tops. In one grouping I saw several Yellow Warblers, White-breasted Nuthatches, Red-bellied Woodpeckers, Baltimore Orioles, Black-capped Chickadees, Red-eyed Vireos, Eastern Wood Pewees, an Eastern Phoebe, and a Scarlet Tanager – all within the space of a few minutes. The Pewees were especially noticeable today all around the site – calling from all directions. I love to watch these birds forage – sitting on a branch just below the understory and then sallying out to nab a flying insect before returning to another perch. I try to image them in the rainforest of the tropics, perching in an understory that’s way off the ground.

Watching them, I got the feeling that this wasn’t just casual foraging. They were busy, eating to put on fat, getting ready for the big flights to come. In another month some of them could be in the southern States or even Mexico. No matter how many birds I see, I just can’t get over the feats of migration of creatures that can weigh as little as 10 grams.

The physical challenge of such a migration is enormous. But there are other, just as challenging, hurdles to be overcome. One of these is predators. There was a pair of Sharp-shinned Hawks around this morning. I first noticed them when I heard the young one making ‘begging’ calls at its nearby parent. This bird flew off and minutes later I saw it return with a small bird in its talons. All along the migration route and on their wintering grounds birds are faced with predation – sometimes involving predators that they’ve never encountered before. For example, in the tropics snakes are much more common, even in the treetops. (I remember in Costa Rica coming across a Vine Snake – incredibly thin for its two and a half foot length – and coloured just like the native vines. When I touched it, it took off, up the vines into the treetops at a surprising speed. ‘Our’ birds have never encountered anything like that.

Given the challenges, it’s little wonder that mortality of young birds in the first year is over 80%.

As I said, the action was in the tree tops and, thus, not around the nets. Given the activity the banding numbers were quite disappointing.

Banded 12:
1 Eastern Kingbird (the first Kingbird banded this year)
3 Black-capped Chickadees
3 Yellow Warblers
1 Common Yellowthroat
2 Northern Cardinals
2 Rose-breasted Grosbeaks

Retrapped 3:
1 Northern Cardinal
2 Song Sparrows

ET’s: 51 spp.

Rick

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