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Archive for July, 2012

If you are going on a long auto trip you want to maintain a steady speed.  One of the earliest indications of the speed that birds can maintain during migration dates back to the early 1600s.  A Peregrine falcon belonging to King Henry IV, King of France from 1589 until 1610, escaped from Fontainebleau and was recovered the next day in Malta, 1340 miles away.  The bird had maintained an average speed of 55 miles per hour for 24 straight hours –  that is a good safe speed, below the legal speed limit on InterState highways.

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Frequent airline flyers know the fastest way to get to where you are going is flying non-stop.  The more stops you make, the longer the entire journey takes.  The same holds true for birds during migration.

Am. Golden Plovers take a non-stop approach to migration.  After nesting on the tundra of Alaska and Canada, they assemble in Labrador, then travel non-stop over the open waters of the ocean to the coast of Brazil, one long flight, about 2400 miles, with no stops along the way.    It is the fastest way to get to S. America but a dangerous flight especially if they encounter bad weather along the way.

The Ruby-throated Hummingbird is my favorite non-stop migrant.  It may not fly as far as other migrants, but it only weights 1/8 of an ounce.  The tiny hummingbird in your backyard flies down to the coast of Louisiana where it spends some time eating and building up energy for a longer flight.   Because hummingbirds have the highest metabolism of all birds, they normally need to eat every 20-30 minutes.   Still, after they have replenished their energy reserves, the hummingbirds take off on a non-stop flight from Louisiana to Central America 500 miles across the Gulf of Mexico.  The trip takes a full day of continuous flying over open water.

The champion non-stop migrant is the Bar-tailed Godwit.  Each fall it flies over 7,000 miles non-stop from Alaska to New Zeeland.  This incredible journey takes several days and a lot of wing flapping

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We usually think of migration as an autumn event.  When the weather starts to turn colder, birds think about heading south to warmer climates.  But the actual migration trip may take some time, particularly if you will be travelling a very long distance.    And shorebirds generally are long distant migrants.  So they do not wait until fall to begin their southern journey.  They actually start in what we might consider mid-summer, July and August.

Last week (July 16th), for example, temperatures were in the 90s, certainly not fall weather.  But there were over 4,500 migrating shorebirds on the East Pond at Jamaica Bay National Wildlife Refuge.  17 different species were seen although the majority of them were Short-billed Dowitchers which are starting their migration to S. America.

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Migration Routes

The Arctic Tern holds the record for the longest migration, nesting above the Arctic Circle and then traveling south to spend the winter below the Antarctica Circle, an annual roundtrip journey of over 24,000 miles.

That is a lot of flying.  But to me, the route they take is more interesting than the mileage itself.  Arctic Terns that nest in eastern Canada start their southward journey by first crossing the Atlantic Ocean to Europe, then fthey fly south along the western coasts of Europe and Africa to the Antarctic Circle.  In spring, they do not take the European route but return flying straight north through South and North America.

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The southern hemisphere is just opposite of the northern.  When it is winter here, it is summer down there.  Water drains clockwise in one hemisphere and counter-clockwise in the other.  (actually that isn’t true but many people think it is)  Even non-birders know that before cold winter weather arrives in Canada and the northern states breeding birds migrate southward to warmer climates.

But what about birds that breed at the very southern tip of South America, down near the Strait of Magellan?  Surprisingly Tierra del Fuego is the same distance from the equator as Nome, Alaska is.  When winter weather arrives down there, do those birds migrate northward to warmer weather? 

Yes, they do.  Called Austral Migration the birds head north as there winter approaches just as our birds head south.  This migration is not as well studied as the one we observe, but scientists know that at least 220 species participate in this reverse migration.

It seems odd to think about birds heading north for migration.

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Even in ancient times people were observant of the birds in their neighborhood.  But sometimes their close observations led to incorrect conclusions.  For example, ancient Greeks noticed that they always saw swallows in spring and summer, but they never saw them in winter.  Their conclusion was that in fall swallows buried themselves in the mud at the edge of ponds and waited for spring to arrive.  And sure enough, when spring arrived swallows first appeared near muddy ponds, not appearing over larger lakes until the weather was even warmer.  What more proof do you need that swallows spend the winter buried in mud?

Today we know a lot more about migration but we still do not know everything.  We don’t know for sure how birds navigate during migration.  I knew a bird bander in Chicago who claimed he netted the same bird in his backyard 5 years in row.  This was a bird that migrated to S. America every year and still managed to find it way back to his backyard thousands of miles away.  How?  Without a Google map I get lost just driving around the block.    

Or how does a newly born bird know when it is time to migrate if it has never done it before?  Or where to go if it has never been there before?

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Whoooo …

Most people, event non-birders, are enthralled by owls.  Why?   Maybe because they are birds of the night and seldom seen.  Or maybe it is because their forward facing eyes project a human-like quality.  Or maybe it is their totally silent flight thanks to unique feathers.

Owls, like people, come in all sizes, large and small, but with a great size range.  The smallest owl, the Elf Owl found in Arizona, is only about the size of a sparrow, 5-6 inches long and weighs about the same as a cardinal (1.5 oz).

 

 

The largest owl in the US in terms of length is the Great Gray Owl which measures well over two feet longer.  However, in term of weight the largest owl is the Snowy Owl which weighs about 64 ounces.

7 species of owl are commonly found in Westchester:  Barred Owl, Great Horned Owl, N. Saw-Whet Owl, Long-eared Owl,  Screech Owl, Short-eared Owl, and Snowy Owl.

How many owls have you seen?

 

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