Saturday, September 10, 2011

Fall Migration

After a few weeks of slow migration, the past two nights have been excellent for bird movement. Although I have not seen a tremendous number of birds in the mornings, I have certainly heard huge numbers of thrushes migrating overhead and seen masses of birds on the radar map. While out birding this morning, Scarlet Tanagers were the most numerous migrant. Over the course of the morning, I saw more tanagers than warblers, which is unusual for this time of year. Of the warblers I did see, Black-throated Blue Warblers are the only real "migrant" species, for Ovenbirds, Black-and-white Warblers, and American Redstarts frequently breed around my property.

 Even the male Scarlet Tanagers are plain this time of year. I managed to photograph this individual as it flew overhead.

While watching tanagers fly from tree to tree, I spotted a bird darting over the yard. As it flew, I recognized the bird as a cuckoo by the long tail and wing shape. The reddish color on the wings and the yellow on the bill identified it as a Yellow-billed Cuckoo. It is unusual to observe this species flying in the open, so I was extremely lucky to have the opportunity to watch and to photograph this bird!

 Yellow-billed Cuckoo in flight - note the reddish patches on the wings. This field mark distinguishes this species from the Black-billed Cuckoo.

 If the lighting is good, the yellow on the bill can be very obvious in flight.

Tonight is shaping up to be another great night for migration. A quick look at the NEXRAD map shows a lot of birds moving in the eastern United States, so if you can get out to do some birding tomorrow, there is a good chance there will be migrants around.

Finally, next weekend is Migration Fest at the Lehigh Gap Nature Center. The weekend will be filled with various programs about the annual migrations of our native wildlife, including bird research presentations, Monarch butterfly tagging demonstrations, a hawk identification workshop, and an evening presentation by Pete Dunne. For more information on this event, visit the Lehigh Gap Nature Center website.

Sunday, September 4, 2011

Meet Leonard

On Friday, butterfly enthusiast Billy Weber visited my property in search of a locally uncommon butterfly--the Northern Crescent. There are very few places this far south where this species can be found. However, there is a population in the field across from my house where I find them almost every year. Although the Northern Crescent is currently recognized as a separate species from the very common Pearl Crescent, the two are very similar and extreme caution is necessary when identifying these butterflies in the field.

Northern Crescent
note the large amount of orange on the forewings and hindwings

Pearl Crescent
the pattern is similar to the Northern Crescent, but the orange is more reduced in all four wings

While visiting the property, Billy did not find the crescents for which he came looking, but he did find another cool butterfly, a Leonard's Skipper. This butterfly is a robust, fast-flying skipper of late summer and early fall. This is the only butterfly in this region that has only one brood that comes out late in the season. In eastern Pennsylvania, the first Leonard's Skippers appear in August and continue through September. The phenology of this species is particularly interesting, as it emerges earlier in the northern latitudes to avoid the early frost.

Leonard's Skippers are not particularly rare, but are localized to large fields with their larval host plants. The caterpillars commonly feed on Little Bluestem (Schizachyrium scoparium), but will also feed on other grasses. Apparently Leonard's Skippers are especially attracted to pink and purple flowers, including Phlox and joe-pye-weed (Eutrochium). Unfortunately, meadow habitats with these requirements are declining in this region due to development. As with most species, once the habitat is destroyed, the population begins to fall. It is becoming harder and harder to find this species for this reason.

 Leonard's Skipper
the pattern on the underside of the wings is unique among skippers in this region

This afternoon, I went searching for a Leonard's Skipper in the field where Billy had one a few days before. After searching through large patches of blooming flowers, I finally found on nectaring on goldenrod (Solidago) flowers. This individual allowed me to take a few photos before it flew off into the center of the field.

 Leonard's Skipper

The Leonard's Skipper belongs the to genus Hesperia, a genus of skippers that are usually marked with a distinct chevron-shaped pattern of dots against a brown or orange background color. They all live in grassland habitats, and their caterpillars likely feed on the same or similar grass species. In Pennsylvania, we have three Hesperia species (in order of flight time): Cobweb Skipper (Hesperia metea), Indian Skipper (Hesperia sassacus), and Leonard's Skipper (Hesperia leonardus). Cobweb Skippers appear in early spring as the warm-season grasses are beginning to pop up from the ground. This species is declining rapidly across its range and is a real treat to find.

 Cobweb Skipper

Indian Skippers are the next to appear, usually around the end of May. This species will live in the same habitats as the Cobweb Skipper, but is more of a generalist, so it will inhabit a wider variety of habitats. Despite the wider habitat diversity, Indian Skipper populations are also declining. In late May, I have seen Cobweb and Indian Skippers flying together in a relatively undisturbed upland bluestem meadow.

 Indian Skipper