I’m at the last point count station of the day, near the saddle of a ridge, at the top of a draw. The mature mixed conifer-oak forest is humid and dark after a late spring rain. And it’s quiet, in contrast to the dry live oak and manzanita chaparral nearby. As I start the count, I hear the cacophony of bird song below me, of birds I passed and already counted on the way up the ridge. Two Black-headed Grosbeak males singing full volume, interrupting each other. And another to the west a few hundred meters. The lilting mutter song of a Western Tanager compliments them, and a very distant American Robin adds a thrushy vibrato background. And what, more than hormones, has agitated the grosbeaks, are two Northern Pygmy-Owls, their long carrying toots, echoing back and forth across the ravine. These small and ravenous predators are something feared by songbirds. A Mountain Quail’s “quark” song begins to match the tempo of the owls’. A clan of Steller’s Jays, who’ve been keeping watch on the owls, give “took-took” contact calls, in tempo and tone matching the Pygmys’ “poot”.
Sonic chaos? Not quite. This is orderly avian communication during the busiest time of year. Reproduction is the foremost goal of every bird here, and singing males and territorial birds represent a generation being produced. The number of breeding adults is an accurate measure of an avian population’s health and I’m here to take that measurement. Point counts, in this case five minutes long with a distance to bird estimate, are an ideal standardized way to collect data. Arranged in transects of 12 permanent points through contiguous habitat and combined with vegetation data collected with birds’ use in mind, point count data can give a quick view of a location’s avifauna or a long term record of population trends.
Now a minute into the count, finally a new bird; the thin airy “seep” of a Brown Creeper nearby. Maybe the old trees flaking bark is an attractive feature. And another following it, possibly a dependent juvenile. A faint growl-ish call. Hmm. A Red-breasted Sapsucker at a nest? Too quiet, and I’ve heard nothing else to substantiate that. I’ll come back to it. A sibilant rising warbler song. It’s almost certainly one in the Black-throated Gray’s repertoire, though the density of Douglas Firs would suggest a Hermit Warbler, and only four days ago a wave of migrating Townsend’s Warblers flooded the canopy. Two Oregon Juncos twitter, a pair feeding together. And just before the timer goes off, a Cassin’s Vireo’s leisurely one sided conversation starts. A-ha … the faint growler revealed! Maybe the pair is nesting in the ancient Black Oaks, their one-meter diameter trunks reaching up through the thick conifers.
I was here three years ago, same route, close to the same date, and my memory is that Cassin’s Vireos were abundant, but this year the resident Hutton’s Vireos are singing at most points. Are the Cassin’s here but not singing? Did the Hutton’s population explode? Do they avoid singing at the same time to avoid sonic competition? Has the late rain altered the situation? Or is it the warm April different? Earlier flowering and leafing out of plants could mean earlier insect hatches, which would affect crucial food sources for nesting birds. Invertebrates are the backbone of the nestling season (heh!). Or rain and cold late in May could stop migrants short of their usual territories. On top of this, Whiskeytown NRA is being comprehensively managed with prescribed fire, and effects from this will become evident over time as birds respond to changing habitats.
Fortunately, to reduce these uncertainties, this project’s design calls for an astounding 10 surveys over 30 years. This glowing example of true long-term monitoring, reflecting perseverance and insight will help illuminate patterns in a variable and changing natural world.