Monday, October 20, 2014

Raptor and non-raptor count summaries 15-20 October, 2014

Despite the lack of cold weather, the season keeps moving at Hawk Ridge! This past week saw the peak of fall color come and go underneath some lovely flights of birds.

The transition from early to late season raptors is fully underway, as days dominated by Sharp-shinned Hawks are being replaced by Red-tailed Hawk flights. Other species on the way out include Turkey Vulture, Osprey, American Kestrel, and Broad-winged Hawk. A few more of each may straggle through, but the bulk of their movement is past. We wish them all the best during the winter before they head back this way in the spring!

Saying goodbye to these species is made easier when welcoming more Red-tailed and Rough-legged Hawks, Northern Goshawks, and Golden Eagles to the skies over Hawk Ridge. And of course there are always Bald Eagles migrating past!

The period 15-20 October produced some consistent flights highlighted by:

660 Raptors on 18 October including 463 Red-tailed Hawks and 28 Rough-legged Hawks

450 Raptors on 19 October including 167 Bald Eagles, 28 Rough-legged Hawks, and 198 Red-tailed Hawks (including a leucistic adult, see below)

701 Raptors on 20 October including 517 Red-tailed Hawks (including another leucisitic adult) and 22 Rough-legged Hawks

An adult leucistic Red-tailed Hawk. One of two individuals that were detected in the last week. Note that this bird is sporting many pure white feathers but still retains a belly band, a red tail and a few scattered normally-pigmented feathers. This genetic abnormality is much more common in Red-tailed Hawks than in other raptors (though still rare).
The story of the non-raptors in the past week revolves around two families of birds: corvids and finches.

Let's start with the corvids. 

American Crow migration is in full swing along the North Shore this week. And I mean literally on the shore. Regardless of wind direction or speed, sunshine or overcast, the vast majority of American Crow migration sticks right to the shore. This means that viewing can be distant from the ridge, but our vantage there provides an amazing perspective on the scope of some of these migrant flocks! It is really amazing to see hundreds of American Crows strung out in large, loose flocks going all the way up and down the shore. Usually this happens in the first hours of the day, but sometimes crow migration will pick back up in the late afternoon. Peak American Crow numbers this week included 1403 on 15 October, 641 on 18 October, and 617 on 19 October. 

No, those aren't dust specks all over your binoculars, it's a flock of migrating American Crows!
When it comes to migration, Common Ravens take a page right out of the raptor's playbook. In the past few weeks, small groups of Common Ravens have been circling and gliding their way past Hawk Ridge, sometimes accompanying Red-tailed Hawks and Bald Eagles and sometimes in single species flocks. Peak flights of Common Ravens this week included 57 on 15 October, 47 on 16 October, 104 on 18 October, and 74 on 19 October.

Migrating Common Ravens. Note the soaring behavior, long, tapered wings, large head and bill, and wedge-shaped tail.
How do you know if you are seeing crows or ravens? American Crow flocks can contain hundreds or even thousands of birds; Common Raven flocks do not reach these sizes. American Crows flap on a straight line when migrating and do not soar or glide for any long periods; Common Ravens soar and glide like hawks when migrating. 

Common Raven migration is a phenomenon that cannot be witnessed in many places, but Hawk Ridge is certainly one of them! This year, we've been noting many more Common Ravens migrating south than usual. I guess it is going to be a hard winter.

Finches have also been impressing the crowds at Hawk Ridge this week. So far, Pine Siskins and Purple Finches are stealing the show, but small numbers of Red and White-winged Crossbills, Evening Grosbeaks, and Common Redpolls are also being noted. We hope there are many more to come! Here's a breakdown of the finches that passed recently:

16 October: 1170 Pine Siskins and the first Common Redpoll of the season

17 October: 2856 Pine Siskins and 755 Purple Finches

18 October: 1198 Pine Siskins and 124 Purple Finches

19 October: 4762 Pine Siskins and 1433 Purple Finches

20 October: 2795 Pine Siskins and 2241 Purple Finches and the first White-winged Crossbill of the season

That's nearly 13000 Pine Siskins and 4500 Purple Finches just in the past week! The Purple Finch flight on the 20th represents a new high count for Minnesota.

Pine Siskins. Note the short, notched tail, dark streaked body, and yellow wing-stripe.
Finch flocks can move past quickly and give only fleeting looks, so how do we know what we are looking at? Here's a few tips for telling Pine Siskins from Purple Finches:

- Use your ears! All finches often call in flight and this can be an aid to both detection and identification. The common Purple Finch flight call is a hollow "pik" which differs substantially from the nasal "skew" of Pine Siskins.

- The behavior of a given flock of finches can provide lots of clues as to the identity of it's members. Pine Siskin flocks move fast, stay in very tight groups, and individuals frequently change position within the flock and often chase each other. Purple Finch flocks move slower, are arranged in looser groups, individuals change position less frequently within the flock and don't engage in chasing behavior as frequently.

- Purple Finches are larger than Pine Siskins, but this can be surprisingly difficult to judge, especially when you do not see the two species side by side. I tend to think Purple Finches look front-heavy, almost as if they smashed into something and most of their body mass was forced to the front. Pine Sikins, on the other hand, look rather slender. The yellow wing-stripe on Pine Siskins can be surprisingly hard to see under some conditions and really obvious in others.

- If you can see plumage details, use them! Often finches will appear as silhouettes, and we are forced to use size, shape, and behavior to identify them. But if you see the raspberry color of a male Purple Finch or the yellow wing-stripe on a Pine Siskin, you're all set! If you see a definitive plumage character on one individual in the flock, use this known individual as a template to judge the rest of the flock. Do they all look the same? Or is it a mixed flock? 

The best way to get better is lots of practice! The birds are here! Are you?

Purple Finches. Note looser flock structure. Individuals do not chase each other or change position within the flock as much as Pine Siskins.
Pine Siskins. Note tighter flock structure. Individuals chase each other and change position within the flock frequently.

Male Purple Finch. Note the short, notched tail, raspberry color, and front-heavy appearance.
Steve Kolbe
Assistant Counter

1 comment:

  1. Steve! Great to see you still afield! Say hello to Frank for me- what a fantastic place to count hawks, eh!?