Droppin' Some Science

It's a good thing that I didn't try to put this together yesterday, because this software does not display its own tables (or even imported ones) properly.  And Acrobat isn't working with Word for some reason.  After about two hours of software updates, I gave up and realized that copying/pasting a table from Word into PowerPoint and subsequent conversion to a JPEG file seems to do the trick...

Anyway, I wanted to organize some of my yard count data to look at how the number and identity of birds changes from winter to spring.  I decided to use my FeederWatch counts from January 13-14 (below-to-slightly-above freezing, light snow cover), March 17-18 (morning temps in the 40s and 50s, trees/bushes beginning to bloom), and this weekend (morning temps in the 40s and 50s, trees/bushes in full bloom).  Counts began at approximately 30 minutes after sunrise for a total of four hours (~2 hours on each day).  Counts represent the total number of each species seen at one time, to avoid double-counting the same individuals.

The one obvious trend is the total number of individuals observed dropping significantly from winter to mid-spring.  While this is due in part to some winter-only species migrating northward (Varied Thrush, Townsend's Warbler, Myrtle Warbler), many of the "year-round" species exhibit the most significant decline.  Bushtits do not find nearly as many small insects and spiders hanging around in the middle of the winter, so they raid my suet feeders in large flocks.  Dark-eyed Juncos switch their diet from insects to seed in the winter and, if I happen to foget to put thistle or sunflower chips on the ground for them, their hunger sometimes overrides their terrestrial feeding habits and they eat out of hanging feeders.  I haven't seen a single Red-breasted Nuthatch - one of my most reliable visitors in the winter - at my feeders over the past two mornings.  But I did see a couple foraging for insects in the neighbor's trees yesterday afternoon.  Anna's Hummingbirds are almost always at my nectar feeders at the first crack of light on cold winter mornings, but now I may not see them until a couple hours after sunrise.  Not only are insects more readily-available at this time of the year, but hummingbirds don't have to contend with hypothermia either (they often go into a death-like, overnight hibernation known as torpor to conserve energy).

The other noticeable trend is that the number of different species is higher during the height of migration.  The aforementioned winter-only residents are typically in higher numbers (especially Ruby-crowned Kinglets), the summer residents (Rufous Hummingbirds, Orange-crowned and Wilson's Warblers) begin to arrive, and others such as Spotted Towhees become more numerous (and vocally-conspicuous) as they seek to re-establish their breeding territories.  And sometimes, you just get lucky:  I'm seeing a lot of Lesser Goldfinches right now because they most likely built a nest nearby and I still don't know why I saw a lone Pine Siskin on Saturday.

Since you're probably as sick of analyzing data as I am, I'll close with a nice picture of a male Downy Woodpecker on my new tail-prop feeder.  Another feeder is on its way shortly.  Stay tuned...

• Posted at Sunday, May 20, 2007 06:58 PM
• In General Category | Permalink