Thursday, October 25, 2007

Raptor migration in the hills

Yesterday while doing fieldwork in La Habra Heights, I was surprised to see a young Northern Harrier sail overhead. These hawks are uncommon migrants in the hills, and a handful may winter. They require large blocks of undeveloped grassland and low scrub, and not surprisingly, have very little habitat left in the Los Angeles Area. Ten years ago, we found them nesting in just one spot in the Puente-Chino Hills - a single pair in the wet grasslands of upper Tonner Canyon, visible from Grand Ave.

Wintering areas are now almost as scarce, and folks should let me know if they run across any this winter. Males are pale grayish above and clear white below, while females and especially first-year birds are brownish below. Both sexes have bright white rumps, which may be seen as they tilt back and forth.

In the same area of La Habra Heights, I also observed an Osprey circling, and then later in the afternoon, another first-year harrier over Turnbull Canyon. Late fall (October) is when hawk migration peaks through our area, and folks may be seeing increased numbers of raptors these days. They aren't being displaced by fires, but are just following well-worn pathways through the sky, heading southeast into Mexico.

Tuesday, October 9, 2007

Butterflies of the Puente Hills

I recently received an inquiry about butterflies in the hills, and want to summarize what we know.

First off, the hills appear to represent an important reserve for native butterfly populations in the L.A. Basin, with 40 species confirmed and a handful of potentially-occurring ones. Diversity of species, not surprisingly, is highest where there is an intersection of major habitat types together, such as willow thickets next to oak woodland next to cactus scrub. Numbers of individuals are dependent on the availability of flowering plants, and some specialized species fly only where their foodplant is in flower.

Not much is known about the distance butterflies can move. A few engage in long-distance migrations, most famously the monarch, but others probably spend most of their lives around the same small patch of native scrub, generation after generation. These specialists are of great concern to conservationists, since their presence often indicates a particularly robust ecosystem.

Many species in the L.A. area fly year-round, but if there's a season when the highest numbers of species and individuals are flying, it's probably late spring (April through June), corresponding to wildflower blooming and warming nights. However, several species emerge through autumn into early winter, nectaring on fall-blooming buckwheat.

In our area, places that attract butterflies include patches of coast buckwheat and mulefat shrubs (only when in bloom), and damp spots along canyon bottoms, particularly if they're exposed to sun. Butterflies will often come to muddy spots in roads to ingest minerals from the soil (most dramatically in the tropics, but also locally).

Most popular gardening books encourage people to plant butterfly-attracting plants to bring butterflies to their gardens, especially "butterfly plant" (a generic term for several species). Several of these are noxious pests (e.g., lantana), which should not be planted anywhere near the open space of the hills. It is better to use native plants (watch for sales at places like Rancho Santa Ana Botanical Gardens in Claremont, or at the L.A. Co. Arboretum in Arcadia), or if your neighbors will stand it, let a portion of your backyard turn "wild" and see what comes in. Just tell them the butterflies made you do it.

A couple websites:

Friday, October 5, 2007

Restoration monitoring preview

One of the goals of all the scrub, woodland and grassland restoration in the Puente Hills is to provide habitat for declining wildlife species. Yesterday, I stopped briefly at the Harbor Blvd. undercrossing to look for scarce lizards in the afternoon heat. While I didn't find these, I did flush a Rufous-crowned Sparrow (pictured) foraging in the native bunchgrasses that were planted as landscaping around the undercrossing (west side of Harbor Blvd.). A large population of this sparrow is found in the scrubby grassland just east of Harbor Blvd. on the Aera property and adjacent to the Shea Homes development.

This is an inconspicuous species typically detected by voice, and is told from other local sparrows (incl. imm. White-crowned and adult Chipping) by its unmarked wings (i.e., no white wingbars), black "mustache" stripe and white eyering. It has two calls, one a high thin "sseeet", and the other a rough "deer-deer-deer", in addition to its song which resembles a weak House Wren.

In the next year, we hope to initiate biomonitoring all the restoration areas in the hills (there are over a dozen) and find other sensitive species like this sparrow using them.