Saturday, February 7, 2009
PURPLE MARTINS CONT’D
My previous post about the purple martin house next door brought some great comments and questions, so I decided to do a follow-up post. This is pretty interesting stuff. It always intrigues me how some species end up being generalists that can adapt to a wide variety of habitats and food sources (coyotes, seagulls come to mind) while others become specialists, and put all their evolutionary (and perhaps literal) eggs in one “basket” (like giant pandas or the sword-billed hummingbird, which has evolved and extremely long bill, and feeds only on Passiflora mixta, and possibly a very limited number of other passionflower species).
When I was looking up purple martins for my post, I discovered what many of you already knew – purple martins are extremely picky about where they nest, and rather limited in how they eat. Here are purple martins at a glance:
FOOD – Purple martins are aerial insectivores. While they eat a wide variety of insects on the wing, they are very susceptible to starvation in just a few days of continuous bad weather. Here on the lake, it’s very easy to have a number of consecutive days of cold wet weather when all the flying insects are grounded. Here’s a list from the website of what they have been known to eat. Unfortunately, mosquitoes seem to be an “urban legend” –
"…dragonflies, damselflies, flies, midges, mayflies, stinkbugs, leafhoppers, Japanese beetles, June bugs, butterflies, moths, grasshoppers, cicadas, bees, wasps, flying ants, and ballooning spiders. Martins are not, however, prodigious consumers of mosquitoes as is so often claimed by companies that manufacture martin housing. An intensive 7-year diet study conducted at PMCA headquarters in Edinboro, PA, failed to find a single mosquito among the 500 diet samples collected from parent martins bringing beakfuls of insects to their young. The samples were collected from martins during all hours of the day, all season long, and in numerous habitats, including mosquito-infested ones. Purple Martins and freshwater mosquitoes rarely ever cross paths. Martins are daytime feeders, and feed high in the sky; mosquitoes, on the other hand, stay low in damp places during daylight hours, or only come out at night. Since Purple Martins feed only on flying insects, they are extremely vulnerable to starvation during extended periods of cool and/or rainy weather."
NESTS – when it comes to where they live, martins seems to be even more limited; they’re very picky.
· Location (very specific restrictions as to the placement of nest condos!). See website if you're interested.
· House must be white, or very light-colored (but colored trim is okay)
· They will abandon an established site it is significantly altered. If you house is getting old and needs replacing, put up a new one nearby until they are used to it, and some are occupying it, then take the old one down.
· Martins are prey for just about many birds and land critters. All houses should have a baffle on the pole to prevent squirrels, raccoons etc from climbing up.
· “Landlords may need to lower housing daily to evict nest-site competitors, or to check on martin nestlings. Systems that telescope up and down, or raise and lower with a pulley and winch, are the most practical. Nest checks will not cause martins to abandon their nests or their colony site” – but any sparrows moving into the adjacent units will!
· There’s a huge paragraph at the website on how to deal with nest site competitors. It sounds like a lot of work and monitoring. A telescoping or pulley system would be essential. So would not having a full time job or a family!! I’ve come to the conclusion that nice as martins may be, I’m not sure I’m cut out to be a “landlord.” I might be tempted to hang up a hollow gourd or two (painted white, of course!) but the question remains – would I have the nerve to evict any other birds who moved in that weren’t martins? Starlings or sparrows, maybe, but what about tree swallows or a flycatcher? Sigh. I think I’ll leave the purple martins to their own devices; they seem to have managed all this time on their own.
Martin photo from Wikimedia commons