Saturday, October 17, 2009


In most autumns, the Rabbitbrush and Desert Broom burst into bloom, and they are both fabulous butterfly attractants. This year, after our very light monsoon, flowers are scarce around Portal, Arizona. But last week, Noel Snyder noticed an especially fine mass of Rabbitbrush blooming along the road from Lordsburg to Silver City in New Mexico. So we have set out with our friend Dick Zweifel, retired curator from the American Museum of Natural History, to learn what butterflies might be flying.

Rabbitbrush, Chrysothamnus nauseosus (Photo by Narca)

The answer is close to being negative data! Very few butterflies are flying at all this year, even where the Rabbitbrush is in fine fettle. It's the poorest butterfly flight year in the memory of local experts. Once again we are seeing firsthand the dramatic effects that drought can have, especially in a region that receives only modest precipitation even in fairly good years.

Another example––on the nearby Peloncillo Christmas Bird Count, Brewer's Sparrow numbers went from an all-time national high count of 13,462 in 2000, to zero just four winters later. These extreme fluctuations in populations responding to drought and flood argue strongly for long-term studies of wildlife! How can we understand a population unless we investigate the full cycle of bounty and stress?

American Snout on Desert Broom, Baccharis sarothroides (Photo by Narca)

On this field day, only American Snouts are flying in good numbers. Perhaps 60 are swarming around the Desert Broom, which is interspersed with Rabbitbrush. Here is a tally of the other butterflies: Checkered White 3; Orange Sulphur 5; Southern Dogface 1; Dainty Sulphur 1; Western Pygmy Blue 1; Variegated Fritillary 1; Painted Lady 4; and Monarch 2.

Only nine species! Last year, Dick recorded 40 species of butterflies at a single patch of Rabbitbrush!

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