February 27th – A (Fairly) Effective Defensive Manoeuvre

Yesterday (Saturday) was the Ontario Bird Banding Association’s AGM. It’s always sort of energizing to meet up with old friends and colleagues, to meet potential new colleagues, and to share banding experiences. But this year was even more so as most of the members of the Ontario Snow Bunting Team were present and we had a chance to compare notes on our bunting exploits (and to possibly recruit a couple of new members from other parts of the province).

This energization carried over to this morning – I’m quite aware that the number of potential bunting banding days are dwindling. I got to the site early (7:10) and with expectation given that we’d had a fresh snow fall and that the temperatures were below freezing (though not for very long). And the birds didn’t disappoint. There was a mixed flock of ~40 birds waiting on the used up bait piles and this quickly swelled to 150-200 as soon as they saw my car stop by the roadside – it’s always a wonderful feeling to have them fly in all around you, sometimes within just a few feet. By 9:00 AM, when Nancy arrived, I had banded just over 50. But then things slowed down. I looked up from my banding efforts in the car and there, on top of one of the traps, was a Peregrine Falcon! Nancy chased it off and it flew into a tree top at the edge of the field about 100 m away. From there it withdrew even further to a treetop some 300 m away. But it was watching. I released a Snow Bunting and it flew north toward the first tree the falcon had been in. The Peregrine launched itself right away and was quickly in pursuit. The bunting dodged back and forth but always worked at gaining altitude. Several times I thought the game was up for the bunting but each time it dodged at just the last nanosecond – but always worked at gaining altitude. It appeared to me that the falcon was having a hard time chasing when the bunting was above it; it seemed to be labouring to gain height while following the dodging of the bunting and after a chase of about 200 m the Peregrine broke it off and flew away and we didn’t see it for the rest of the day.

The activity of the Peregrine attracted an American Kestrel and it sat around on an elevated perch waiting. It also started a chase of a released bunting and, again, the bunting took the same tack as the other – it dodged back and forth but always climbing to get above the pursuer. And the Kestrel seemed to have the same difficulty; that is, gaining height while trying to follow dodging manoeuvring. Thinking back to the many other chases I’ve witnessed this season involving Kestrels and a Merlin, the tactic has been the same. I have seen over 30 chases and have never seen a kill when the prey bird got higher than the falcon. I would like to understand the aero dynamics of this phenomenon. Does the necessity of climbing while dodging back and forth cause the falcon to slow down to a point that it “stalls”? The falcons seem to be labouring when trying to climb in these situations. Every successful kill I’ve witnessed has occurred when the falcon has come in low (and consequently often hidden from the flock until the last moment) and very fast and has burst into the midst of the flock almost before they saw it coming. Kills have been on the level, as it were.
The bottom line bunting banding-wise though is that things slowed down.

We banded: 93 Snow Buntings, 4 Horned Larks, and 9 Lapland Longspurs

We retrapped 41: 11 Snow Buntings, 30 Lapland Longspurs

Rick

1 thought on “February 27th – A (Fairly) Effective Defensive Manoeuvre

  1. I understand that falcons kill/disable their ariel prey with a high-impact swat with their feet.
    Sibley says: “(PEFA)..catch(es) its prey at the bottom of vertical dives launched from high in the air.”
    It’s good to be on top.

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