22 November 2009 – 1 Nashville Warbler

Found a late (unfortunately, too late) Nashville Warbler today.

Photo by Bob Mulvihill, Powdermill Nature Reserve

According to the “Date Guide to the Occurrences of Birds in Oklahoma” (5th edition, 2009), we expect that most Nashville Warblers have left the state by 25 October, so this bird is several weeks behind schedule. It’s destination for winter:

This bird was not in fresh condition like so many of the birds I find. It was still feathered, but its eyes had sunken and the flesh had dried out some. Its condition was exacerbated by the fact that its feathers were badly matted from being soaked in a recent rain. It hasn’t rained for at least 24 hours here in Stillwater, so this bird might have come through several days ago. (I found it in a section that is difficult for me to access on a routine survey, so I might have overlooked it earlier this week.) So the “late date” for this bird is very likely not Nov. 22, but it’s probably no earlier than about Nov. 17.

Solutions for window collisions?

People often ask what they can do to reduce bird/window collisions. While the magnitude of the problem is great, there are somethings we can do to reduce the current – and future – carnage.

The basic problem is that birds don’t recognize glass as a barrier. Anything that communicates “barrier” to a bird solves the problem. Those old falcon silhouettes don’t really help, unless you put up so many that the glass is basically covered. Narrow strips of fabric or some other kind of opaque material will work but, again, they need to be covering probably more than 2/3 of the window area to do any good. Recently, some folks have had some success using UV markers or other colorings – birds can see them but humans cannot. But the jury is still out on how effective such treatments can be. Check here for a link to David Sibley’s blog including his own “field” trial of using a UV highlighter pen to make windows more obvious to birds.

The one product I’ve seen that really has some potential to reduce mortality around homes is Frank Haas’ “Bird Screen.” This is a netting product that can be mounted to an exterior window that should reduce mortality to zero while still allowing a clear view to the outside from inside. Even birds that fail to recognize the barrier with the screen down are safe – they hit a soft netting with enough give to allow them to roll away from the contact unharmed.

I’ve been asked about other structures that could be hung near windows to discourage bird strikes, and I can foresee how some things like this might work. The point would be to either draw attention to the barrier of the objects (e.g., hanging flower baskets?) in front of the window, or at least cause the birds to slow on their approach, rendering any collision that still occurred far less likely to be fatal.

For people with feeding operations, many birds hit windows when they take flight from feeders. The solution to this problem could be very simple: either move the feeders farther away from the windows or move them so close that a fleeing bird that strikes the window would not have enough room to get up enough speed for a fatal collision.
For larger buildings on major migration pathways, lighting can often play a big role in mortality. Check out the Fatal Light Awareness Program (FLAP) for information and resources.

New construction is a whole other ball of wax. New pitted or frosted glass products can allow a view to the outside from within -and bring in plenty of natural light – without leaving a clear reflective surface on the exterior. Construction that angles windows to reflect the ground, rather than sky or trees, can also be effective. Check out how Swarthmore College worked to re-design a science complex that included “bird-friendly” glass in its construction. Links to other examples can be found here.

One of the best resources for solutions to bird strikes can be found at Laura Erickson’s For the Birds blog.

2 November 2009 – no casualties, but . . .

I did find two Dark-eyed Juncos trapped in one of the west side alcoves this morning. As I approached, they each thumped the glass a few times before gaining enough altitude against the wall to turn back around and fly out to safety.

I’m beginning to think that, at the NRC, the odd shape of the building is as much a problem as the reflective glass.