Sunday, April 11, 2010

More about Merlins

The bird pictured above is the first Broad-winged Hawk for Sandy Hook this season, which was seen and photographed at the hawk watch today. They seem to be early this year: practically every other hawk watch, including Great Lakes sites like Derby Hill and Braddock Bay, had their first broadwings last week. I felt my count at Sandy Hook was lagging behind a bit, but then Sandy Hook isn't exactly a buteo kind of place anyway.

And I felt better already after looking at historical data for Sandy Hook. First broadwings last year were 6 individuals on April 13. On the exact same date the year before I had the first 9 for the Sandy Hook Migration Watch. In 2007, the first 2 broadwings were seen on April 21, while the first broadwings of 2006 were spotted on April 15. The first broadwing for 2005 was seen on April 19, and the first 3 BW's for 2004 on April 17. In other words, today's two individuals were the earliest broadwings in recent history!

So these birds were early, but not dramatically so.

What seems unusual to me is this continued push of Merlins, which as far as I can tell no other hawk watch is seeing at the moment. Most sites that post their numbers on are reporting a few Merlins passing through these days. Nobody is reporting the kind of numbers I'm seeing at Sandy Hook.

The BNA account for Merlin cites a 1985 publication in the Journal for Raptor Research by Bill Clark describing Merlin migration along the coast of New Jersey, which found that peak spring migration past Cape May occurs late April (cited in Warkentin et al. 2005). I've dug into the Sandy Hook archives, and they confirm this for the Hook. So, as good as the Merlin flight already has been, it's quite possible - nay, likely - that the majority of them are still to come.

Still, I think it's unusual that only 11 days into April, I'm already at 63 Merlins for the month. Today I had 15, which seems like a lot for early April.

Let's compare that to Merlin numbers in recent years. In the table below, I've summarized for the last 6 years when the peak flight occurred and how many Merlins were seen that day; how many Merlins were seen in the first half of April that year; and how many Merlins were seen that season.

Year peak flight total 1st half of April season total
2010 63
2009 12 on 4/26 12 105
2008 25 on 4/24 15 219
2007 32 on 4/29 16 184
2006 135 on 4/25 61 387
2005 31 on 5/1 0 97
2004 34 on 4/27 13 272

This table shows that the 63 Merlins so far this April are not unprecedented - 2006 was an exceptional Merlin year with similar counts - but quite unusual nonetheless. A peak flight between 25 and 35 in the last week of April seems to be the rule, with exceptions in both directions, last year being the worst and 2006 the best on record.

I'm very curious to see how the season is going to play out for this species, a personal favorite of mine.

Cited literature:
Warkentin, I. G., N. S. Sodhi, R. H. M. Espie, Alan F. Poole, L. W. Oliphant and P. C. James. 2005. Merlin (Falco columbarius), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online:

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