Wednesday, September 13, 2006

Broadwings

Broadwings never do what they're "supposed" to do. Despite the early date, yesterday Hawk Mountain counted over 7000 broadwings, the fifth largest count ever. A few miles to the east at Bake Oven Knob, over 4000 were counted. I only saw one other site that counted over 1000 hawks, the other 30+ sites I checked results for rarely had over 100. So what's going on??

Also, though the wind was largely calm (which broadwings like), when there was a breeze yesterday it was from the south (which broadwings hate). Wind from the south means these birds are moving with a headwind, which means they have to use more energy on their already long and arduous trip down into central and South America.

Interestingly, to me, the Great Lakes hawkwatch sites that often count broadwings in the tens of thousands really haven't seen much yet. In other words, their broadwings so far seem to be arriving (or not) on schedule. So why so many birds in the east this early in the season? Boy, don't I wish I could answer that one.

So I'm going to make a few semi-educated guesses. Although the weather will block migration for the next 3 days, the front is supposed to clear out by Friday and have good skies for flying after that. On the surface of it, the birds shouldn't need to fly in these numbers this early. Something else must be making them want to move early. That something else, in my opinion, is likely food.

I suspect that their food source in the north either wasn't as plentiful as usual, or perhaps it's been cold up north so their food source is vanishing earlier than usual. It's liable to take weeks/months to get a reasonable answer to this mystery. But trying to figure out the "whys" of migration is one of the reasons I find it so fascinating.

4 comments:

pablo said...

7000 hawks! But surely they can't have all been counted by one person. So if more than one person was counting, how do they know they weren't each counting the same bird?

Carolyn H said...

Pablo,

I think I saw that 2 people helped with the observations at Hawk Mountain, but there's always only 1 official counter. They use a clicker-counter to help with the tallys. Also, the birds are migrating, so they are moving in a north-south direction in the fall. Broadwings tend to circle in large groups (called "kettles") and then stream out of the tops of the thermals, often in single file. Usually they can be counted when they are streaming out. Good question!

Lynne said...

I am going to try again at Hawk Ridge in Duluth, MN this fall. I've been there twice before, but on bad weather days with little or no raptor action. Wish me luck!

You have an interesting blog- I've learned lots!

LauraHinNJ said...

Migration is so mysterious and unpredictable!

I had planned to take today off from work to go see broadwings, but it poured rain all day.