Sunday, March 10, 2013

Rarely Do Our Numbers Match-Evening/Day-March 10, 2013

Assisted by: Rose Leong, Pam Alber, Maryjo Churchwell and Joe Hopkins

Migration Today:

Weather today ranged from 52-73 degrees with a NE breeze becoming stronger as the morning progressed. The sky was clear. We estimated the evening count at 100 Swainson's Hawks and today 100 left. Three distinct groups of SW's (72-24-4) departed via Palm Canyon. They streamed west from the Date farm very low. The roosting site of the TV's was unknown.

The photo today is a blow up of a few Swainson's Hawks. We are trying to determine the % of each morph (genetic color form) that pass through Borrego Valley. At this time we are experimenting with techniques to distinguish the morphs randomly through photo's. Accounts of morph's observed in different parts of Western US suggest that Western Swainson's are predominantly dark morph's (dark and intermediate). Only 10-15% of California SW's are light. However, we seem to encounter a larger proportion of lighter morphs in Borrego Valley. This suggests that many of our birds are moving out of California to breed.

Evening Watch:
Only 8 Swainson's Hawks were observed flying into the Date Farm.

The wind should be calm tomorrow. Look for lift-off around 8:30-9:30A daylight savings time (DST). I will use DST from now on through the rest of the season. Remember however, hawk time is one hour earlier. As the season progresses and daylight increases, the hawks will migrate earlier.

Two Light Morph's and one Dark Morph and one unidentified-HC

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