The Dawn Lift

Every once in a while spring migration brings a south wind for birders to enjoy and birds to take wing with.  This morning brought a pretty decent south wind and warmer temperatures AND actually provided some bird migration.  Tuesday, April 3, was a pleasant morning to witness the return of the blackbird flocks.  Some of the other migrants that are usually present in low numbers were also seen today, including Lapland Longspurs, American Pipit, and Horned Lark.

The migration was also well represented on the radar last night.  For folks that don’t know, you can follow the nightly migration of birds here.  The concentric donuts that appear during south winds represent birds and insects migrating northward.  This donut will disappear with dawn, as birds spiral downward back to earth after a night of migration.  A typical pre-dawn shot, taken last night around 5am central (6am eastern) time is below.

A unique migration phenomenon that is special to coastal areas is the dawn lift or rise that occurs just as the first light appears on the horizon.  Birds, unknowingly flying over the water, will fly upward when they find out where they are.  By rising, they can then turn towards the nearest land they can find.  This leads to an apparent reverse migration, as birders witness birds coming south from Lake Michigan.  Migration conditions were set up to create a dawn lift this morning.  Notice the the blob seen over the lake.  This blob is picked up on the outer reaches of the radar, at a higher altitude then those detected near the radar center.  The image below was taken about 15 minutes before sunrise.

This morning involved a heavy and early longshore flight that quickly died down before 9am.  During four hours of counting today, 6,014 birds were identified, leaving us just shy of 200,000 for the season.  Waterfowl were on the light side, but today saw an increase in many species.  Some of these highlights included: 23 Yellow-bellied Sapsuckers, 122 Tree Swallows, 2 Barn Swallows, 2 N Rough-winged Swallows, 21 Yellow-rumped Warblers, 2 Vesper Sparrows (new for the season!), and 32 Purple Finches (including multiples singing at the green tower site).

Yellow-rumped Warbler at Indiana Dunes SP, April 3, 2012

The local Pine Warbler makes his round each morning, giving his soft trill in search of his potentially arriving mate.  He patrols the main pine stand between the two beach lots, then often moves up hill along the road to the Green Tower site.  He hops along the West Lot Jack pines before returning back to his original pine stand.  During a brief lull, he posed for the counters today.

Pine Warbler, April 3, 2012.

Just as the migration starts to pick up again, mother nature will shut it back down.  Highs will drop to the mid 40s for the duneland area.  South winds are not predicted until Saturday.


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