Naturespeak A naturalist's view of the world

September 17, 2007

A Bird in Hand

Filed under: Uncategorized — wykes @ 8:50 pm

  Each fall there is a migration of African magnitude taking place in S.E. Michigan.  It is as spectacular and awe inspiring as the herds of wildebeest and zebra seen on the Discovery Channel, although it goes on in silence and relative obscurity.  To see it you have to cast your eyes upward and peer into the autumn skies overhead.  Great hordes of raptors – hawks, eagles, falcons, and vultures – stream over our airspace on their southward journey.  These birds come from the Canadian Shield area and funnel over the mouth of the Detroit River by the tens of thousands.  From there they pour down over Monroe County on their way to all points south.

  This funneling point is located at Lake Erie Metropark near Gibraltar, MI. Here you will find one of the premier hawk-watching sites in the country – a place to view the N.E. sky and catch a glimpse of 17 species ranging from the delicate Kestrel to the massive Golden Eagle.  At this crossing point, counters identify the passing flocks and record some pretty impressive numbers.    

  Rather than continue with the superlatives of this spectacular phenomenon, I’ll direct you to www.smrr.net, the web site for the Southeast Michigan Raptor Research group that tracks this migration.  So far this season (which began on Sept. 1) there have been 122,989 hawks tallied, but for now I’d like to direct your attention to just four of these birds.

  We had the golden opportunity to reach up into the migration stream and snatch a few of the travelers during our annual Hawkfest – an event that celebrates this raptor passover. On Sunday, the second day of the event, a Broad-winged Hawk, two Sharp-shinned Hawks, and a Cooper’s Hawk were persuaded to pay us a visit.  These birds were trap netted (lured by the promise of a tethered Starling) and banded for research purposes.  Before being released, however, they were brought over to the Hawkfest location and introduced to a crowd of curious onlookers.

  First up was a Broad-winged Hawk (see here).  This species is truly the star of the fall migration.  Over 73,000 of his kind passed over our site on Saturday and 15,385 would make the scene by the end of this day.  This individual, approximately number 10,244 in the migrant count for Saturday- give or take a few thousand – is a full-sized but immature bird.  Broad-wings are the smallest members of a group of hawks known as the buteos. Adult birds are distinguished by a clearly banded black & white tail and a rufous red-brown chest. Once common in Michigan, these forest hawks have all but disappeared from the local landscape.  This Canadian bird (eh?) will make his way all the way to Argentina by the time his journey is done. Confident that his Spanish lessons were progressing, this senor was bid “adios” and propelled back into the migration stream.

  Next to the Broad-wings, Sharp-shinned Hawks are the most common September migrants.  There have been 3,490 recorded so far this year and on this day they were coming in at a rate of nearly 100 birds per hour.  Over one particular hour, counters ticked off nearly 400 birds.

  We persuaded two young (human) ladies to help us handle a matched set of these birds (see here for the male bird and here to see a female).  “Sharpies,” as they are known to the counters, are members of a class of hawks known as Accipiters, or “bird hawks.”  Of course as hawks they are “birds,” but that Nome de plume means that they eat other birds for a living.  Chances are you’ve seen one of these feeding at your bird feeder (on your feathered friends, not your seed!).

  Both of these temporary captives were immature birds as well, but the male was actually a 2nd year bird. The larger female had the intense yellow eyes and brown streaked plumage that marked her as a first year bird.  In other words she was born this spring.  The male, literally on the other hand, had orange eyes and was gaining the adult plumage which consists of a slate gray back and a red-brown barred chest.  Should he survive into the following year, he will return north sporting bright ruby red eyes.  He has beaten the odds by making it into his second year, while she faces an 80% chance of not surviving until the return trip.

  The male bird had just eaten before his capture and his crop was bulging.  A feather was stuck onto his beak as a souvenir of that meal. We carefully wiped his hooked bill before the photo op and sent both of them skyward to resume their journey.

  Last up for our perusal was a female Cooper’s Hawk (see here).  She also represents the accipiter clan and is a close cousin to the smaller sharpies that preceded her. Like them, she will gain red eyes, slate back and red-brown breast by the time she reaches the age of three and, like them, her chances of making it there are stacked against her.  Many of her kind will stick around to feed on your feeder birds this winter, so please give her the respect she deserves – it ain’t easy being a ‘coop.  Accipiters have short powerful wings (see here) and long tails that allow them magnificent maneuverability when chasing their avian prey through the brush. Look here to see what’s left of a Mourning Dove after an encounter with one of these accipiters (you could say that this was a Mourning dove in need of mourning).

  There are far fewer Cooper’s Hawks in the natural scheme of things than the other two hawks mentioned – that’s just the way it is.  This fall only 78 have been seen flying over. On this particular September day only four made the count, so we were fortunate enough to hold onto 25% of the daily population.

  William Cooper, the 19th century naturalist for whom the bird was named, would have been proud of his namesake as she was released.  After a few powerful wing beats, in order to gain some altitude, she let loose a stream of whitewash as if putting a punctuation mark on her opinion regarding temporary captivity.  A bird in the hand is good for the humans but two in the bush is good for the bird.

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