I like to play a little game with my GPS. I take it with me whenever I travel and when I get to my destination I turn it on. It strains for several minutes trying to locate a familiar satellite before giving up and asking whether I’m inside or under a roof. Coyly I indicate “No” at which point it asks if I’ve moved 100’s of kilometres since I last used it. Bazinga! (I indicate) And it goes on to plot my new location. I was curious this morning to find out how far, in a straight-line direction, I was from the Ruthven Banding Lab. 3,606 kilometres! It would be a lot further than that if migrants chose to go around the Gulf of Mexico rather than across it.
This got me musing on the phenomenon I’ve been seeing in the last few days of migrants heading north along the coast. Right here they can do that but what happens in the NE corner of Nicaraugua when the coast bends to due W? Birds then have a choice: go W and continue to follow the coast; fly NW over water to the Yucatan (and from there where?); or continue flying due N to Cuba and then up through Florida. There are advantages and disadvantages to all of these choices. Along the coast there are lots of predators which the migrant wouldn’t find over water (especially at night) but the water routes require good fat loads and favourable winds (there’s no place to rest!).
What got me going on this particular train of thought was the sighting early this morning of 13 Eastern Kingbirds that were moving along the coast but then suddenly knocked off for the day and dropped into some fruiting trees that Slaty-tailed Trogons were taking advantage of. Also, I spotted another Chestnut-sided Warbler foraging in the scrub – fattening up for the long haul? [Interestingly, I have seen 3 of these warblers in the past week – different individuals, 1 male and 2 females. In all cases they were in association with Lesser Greenlets, a bird that looks like a slightly larger Nashville Warbler and sounds like a slow-singing vireo. Two of these greenlets were putting the final touches on a nest – it was great fun to watch the one grab a strand of spiderweb and jump off his perch, hang and swing, before the web let go and he could take it off to the nest.]
These birds have a long way to go.
Rick