Tuesday, October 23, 2007

Thoughts on Hawk migration. Good and bad days and perfect days.

The migration of any bird is something that not even the best can predict. Where is it coming from? where is going? What route is it taking? where will it land? These are just some of the questions that plague all birders. Even the most expert among us can only give educated guesses. What factors are involved in migration? many things. Weather, food, shelter, predators and habitat just to name a few. Weather seems to be one of the main ones. Sunny days and clear nights seem to be better than clouds or overcast. In fall, N winds are better than S winds. An incoming high pressure front seems to be better than a low pressure front. What do the birds look for and how do they know when to go and when not to? Regardless of whatever may come between them and their goal, the still brave the dangers of travel between their summer breeding grounds and their winter home in the tropics. There are many species that need all migrate and all need food, shelter, good weather. What do Hawks need for good migration movement? It seems that clear sunny skies and NW winds make for the best days. In my post from Tues Oct 9, I mention that it was a perfect day. How little did I know how right I was. After spending the morning in the field, I checked up on the counts at Concordia, Duluth and IL beach SP. Concordia and IBSP were especially good. It seems that the NW winds drive the hawks up to the lake where they can go no farther E and so continue S. on the IL bird list, I recall seeing a post from a guy who had visited the hawkwatch that day for the first time in his life. It was his first hawkwatch. He mentions in his post that they told him to "never to expect another day like that again". "EVER!"
It certainly was a record day. Raptor numbers at IBSP and Concordia broke records that hadn't been broken in years. Duluth also had near record numbers that day.
The weather that day WAS perfect. A low pressure storm system the day before had been cleared that night by an inversion system of high pressure and NW winds. The result was perfectly clear, sunny skies, NW winds, temps in the 60s and a 3 day backup of Raptors that had been held up by the storm system. in other words, a Perfect day. Days like that are rare and few and far between. Most days are good if the weather is. Anywhere between Sept 1 and Nov 10 should have good hawk movement. A good look at the forecast will help in hawkwatch success. Look for a forecast that has as close to perfect as possible. Today for instance, was a good day. Better than most. the forecast was clear and sunny with West winds changing over to NW. What about wind speed? 1-4MPH is too light. There's no enough air movement to make a good migration day. Yes, you'll find birds, but only low numbers as they will tend to ride the thermals and hang in one place. If you want to observe hunting hawks, it might be a good day. 15-20MPH is too strong. The wind will blow the hawks right out of the air. Good luck seeing anything on days like this. Steady winds 5-10MPH is generally good for migration. There's enough air movement to make migration easier but not so strong that Hawks can't fly. Today was a day like that. wind speed, 5-10MPH with gusts around 15-20MPH. Tues the 9th was like that too. Not too strong and not too weak. Just right.
But weather is only a small part of it. I have been out on days that should have been really good and found nothing. I have also been out on days that should have been terrible but were suprisingly good.
What makes them go no matter what? You're guess is as good as mine. I suppose that eventually we will find the answer to most questions but some questions will forever remain unanswered. Though, even as we answer questions, more questions will arise.
Another question is how do birds and animals communicate? We think we know some of their language. However, what we know is only simple deduction after watching actions. How do humans communicate when there is a language barrier? we use universal sign language. Gestures and movements. Birds don't speak like we do. Calls and songs are only a small fraction of their language. What does the rest of their language consist of? sign language. Of a highly developed kind. The slightest look, movement or shiver means something. Where humans have lost the language through our speech, birds and animals have retained it. Their language is far more advanced than we give them credit for. What happens when we inevidably come across an alien race? a race that doesn't speak our language. doesn't understand sign language. How do you communicate? When we figure out how to talk to animals, we will have made great advances to prepare for meeting an Alien race.

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