Naturespeak A naturalist's view of the world

July 7, 2009

Baskin’ Robins

Filed under: Uncategorized — wykes @ 4:59 pm

 The sight of oil-soaked human sun-bathers on a sunny summer afternoon is nothing biologically unusual. They are doing what comes naturally, although they are performing the ritual in a slightly un-natural way (using sun block while purposely baking in the open sun, for instance).  Lots of wild creatures do it, however, so there must be some solid reason for sun-bathing. Humans are far from unique in this regard. Black butterflies do it, solar-seeking snakes do it, warmth-wanting water turtles do it, and yes, your basic birds do it too.

 When birds bask, they assume some very bizarre and un-birdlike poses that resemble human sun worshipping postures as much as anything (see baskin robbin above). One of the semi-worthless facts that I came upon states that over 170 species  of birds have been observed sun bathing. I have to assume that the rest choose private nude beaches. Double-crested Cormorants, one of those “observed species”,  perch with their wings “spread eagle” in order to dry their feathers in the sun. These birds lack the natural oils found in other water birds, so they actually get wet when they dive for fish (see here).  Turkey Vultures will do the same thing, but for different reasons. They spread their six foot wings in order to maximize the surface area exposed to the warming effect of the morning sun. Smaller birds aren’t quite so dramatic, but they do whatever it takes  to expose as much bare skin as possible.

Yesterday, my backyard became a basking haven for all the neighborhood birds. They chose a location where the mid-morning rays of the sun found a gap in the tree cover. Robins, grackles, and even a solitary red-wing blackbird sought out the site for a brief sun worship session. In the view above, you can see a red-wing and a robin so engaged. The robin was flat on his belly -back to the sun – with out-stretched wings and the blackbird was positioned perpendicular to the sun.  He had one wing out, head tilted over, and his mouth was agape. Both of these creatures maintained their respective poses for several minutes before resuming their previous bird-like dignity.  I was able to get a few more shots of another robin doing the belly flop (see below). Not only were his wings out, but his rump feathers were flared open to allow the warmth to penetrate all the way into to the bare bottom skin. In another view (see here) the robin is gaping like the blackbird and flaring his back feathers.

Not that I quote Australians much, mate, but in that country they refer to this behavior as “trancing.”  Indeed, the birds do seem to be in a trance-like state for a minute or two. Studies have shown that a condition similar to heat stress, or hyperthermia, is achieved during this activity. The eyes are at half squint and the bird opens his mouth to pant. “Bird pants” are not blue jeans with a hole cut out of them for the tail, but are actually a series of rapid short breaths. Like dogs, who also do not wear pants, birds can’t sweat so they have to get rid of excess heat from their mouths. Staying in such a state for too long could be dangerous for these very warm-blooded creatures, so they limit their exposure periods to just a few minutes at a time. Basking birds deliberately select still bright days with temperatures over the mid-70’s F.

Since tanning and baked beauty is not at stake, one might wonder why birds risk these potentially dangerous trances. Apart from the physiological danger, the momentary ignorance of predators could also prove fatal. The answer is…well, we don’t really know. Since reptiles bask to acquire vitamin D, it is likely that their feathered cousins do the same for the same reason. This would explain why the skin is exposed by lifting the feathers. Another equally likely reason is ecto-parasite removal. By introducing warm dry drafts into their nether parts, birds might cause mites and other pests to scurry about. After basking, the bathers do spend quite a bit of time preening as if plucking off heat-offended ticks!

It’s worth noting that birds worship the same sun that we do. Watching them is something like peering into our primitive past long before there were tanning booths and SPF’s.

1 Comment »

  1. I’m so happy to read this entry, which will, I think, solve one of our bird mysteries. We’ve noticed this behavior in our feeder-birds (those that come to our feeders, not those we feed upon). They crouch down on the porch railing in full summer sun and just stay that way for a while. They only hunker down in the really hot zones, which get Pretty Darn Hot here in Texas in July.

    When summer arrives again (which could be next week, who knows?), I’ll watch them to see if there’s any post-searing preening going on.

    Comment by Joy K. — March 7, 2010 @ 4:59 pm

RSS feed for comments on this post. TrackBack URL

Leave a comment

Powered by WordPress