from the Garden

 

Q. How quickly do migrating birds return to our part of the world?

 

A. Much more quickly than we thought just a few years ago. Recent work by Canadian ornithologists shows birds urgently return to Michigan - and their breeding grounds - in spring.

 

Researchers have developed data recording backpacks weighing less than a dime. They strapped packs on the backs of purple martins and wood thrushes to document their migration. What they learned shocked the ornithologists. All the birds made the migration in less than a third of the time than they expected.

 

The research found the birds covering more than 300 miles a day, an average of 12.5 miles per hour versus the expected 90 or so miles per day that was expected. This pace is far faster than these birds use in fall, when they cover 90 or so miles a day. Martins and thrushes were used in the study (Martins migrate in daylight, thrushes at night.). One martin equipped with a backpack left Brazil in April and reached its breeding site in Pennsylvania in just 13 days. The same martin took 43 days to return to Brazil in September. It had been assumed that migration in both directions was accomplished at the same pace. That kind of speed is amazing since a small bird's travels consume the majority of body fat they pack on each day. What's the hurry? The males generally lead the migration. They are literally racing with the other males to claim the best breeding territories. So even though flying so fast may leave them exhausted by the time they arrive here, the earliest males claim and defend a nesting area against the slower migrants. 

The new ultra lightweight data devices record exact sunrise and sunset times as the birds fly. When these data are downloaded, researchers are able to pinpoint the birds' location each day, documenting exactly how fast they're flying.

We now know for instance that birds leave their winter range in Central and South America later than had been assumed. Instead of heading north in March, it turns out that martins and thrushes don't leave until April. The fast pace of the move north makes having reliable stopover sites along their route even more important than assumed. The Red Knots timing of their stopover on Chesapeake Bay to coincide with Horseshoe Crab reproduction is a more common example than previously thought. Birds in a hurry need to find food right along the expressway. They don't have time to search for good eats. Martins need to find a good supply of large flying insects to keep them going, and thrushes forage on the ground for insect-rich meals.

 

It helps those of us who care about birds have a better understanding about the threats that loss of habitat and climate change pose for birds. And it helps bird-friendly organizations like the American Bird Conservancy establish conservation measures to mitigate those threats.
 
Q. I've heard nyjer seed referred to as thistle.  Are they the same thing?                
 
A. No, they are not the same plant. Thistle is a wildflower unless it is growing in your yard, where it becomes a weed. Even though there is little human affection for the plant many birds love it. Goldfinch are often seen pulling seeds from the ripe heads of the plant or using the downy material from the head for nest building. Nyjer, on the other hand is a relative of the sunflower that is grown in semitropical climates. 

 

The majority of it in this country comes from Burma, India, Nepal and Ethiopia. It has been mistakenly called "thistle " for so long that the term has become common usage. Nyjer enters the U.S. through two ports, one in New Jersey and the other in Louisiana. All imported nyjer is sterilized at the port to kill the parasitic dodder plant that is associated with nyjer. 

The heart to shell ratio is very favorable and tends to offset the price paid for this seed. That being said nyjer is likely to be in short supply this summer and if it's available is going to get expensive. India and Burma are major exporters of nyjer (none is grown in the U.S.) and it seems they are attempting to drive the price up by withholding this year's crop. As a result the use of "finch mixes" or sunflower hearts will undoubtedly become more common as we move through spring.