Wednesday, June 24, 2009

Early Season Dragons

12-Spotted Skimmer (male)

Dragonflies have become a very common sight over ponds, streams, wetlands, and fields over the past few weeks. Many people are familiar with these insects as a group but are less likely to recognize one individual species from another.

Watching and identifying dragonflies is similar to learning to identify birds. Most of them have similar shapes and sizes with small details of appearance or behavior that set species apart from one another. Even males and females of some species are different in appearance.

One of the most remarkable facets of these incredible insects is their unique lifestyle. Similar to the way a frog begins its life underwater, so it is for the dragonfly. All during the summer, adult dragonflies can be observed mating above and laying eggs in many of the area's bodies of water. The eggs eventually hatch and the dragonfly lives the first half of its life as a nymph underwater.

Dragonfly nymph

The nymphs breathe oxygen from the water through a set of gills located inside the abdomen, or rear portion, of its body. During this stage of its life, the nymph is interested in one thing: Food. Dragonfly nymphs are predators and spend much of their time eating other members of the pond community, usually other insects, worms, snails, tadpoles, and small fish. Of course they're not immune to becoming a meal for one of the pond's fish, frogs, turtles or birds. The nymphs will continue to eat and grow, shedding their exoskeletons many times, for as little as a few months or as long as a few years. Once the time is right, the nymphs will crawl from the water to a sheltered location and shed their nymphal exoskeleton one last time.

Dragonfly nymph exoskeleton

Once the dragonfly emerges from its nymphal exoskeleton, the body and wings unfurl, the blood begins to pump, and the new exoskeleton must harden before the adult dragonfly can effectively take to the sky. Once it becomes airborne, the dragonfly patrols the skies for all manner of potential prey. Mostly opportunistic, they will take flies, midges, butterflies, damselflies, and other dragonflies. They themselves often become prey for birds, frogs, fish, and spiders. The life cycle begins again when the newly emerged adults mate and lay eggs.

So here are a few of the dragonfly species seen recently around the sanctuary:

Common Whitetail (female)

The Common Whitetail is one of a number of species of dragonflies in which the mature males and females look quite different. The females have brown bodies with yellow-ish markings on the sides of the thorax and abdomen and and black patches on the base, middle, and tips of all four wings (see below).

Common Whitetail (female)

Male Common Whitetails are very similar to females as immature adults (see photo below). The biggest difference is the pattern of black on the wings. Males have only the large patches on the middle of each wing (hidden by my thumbs in the photo) and small bars at the base. As they age, the male's abdomen will turn a chalky white color.

Common Whitetail (male)

Common Baskettail

The Common Baskettail is pictured above and below. This species is difficult to identify due to it's rapid and erratic flight. They often fly in swarms over fields, forest clearings, and other similarly open areas. So in this instance, the dragonfly's behavior, not it's appearance, is one of the best clues to it's identification. In this case, an insect net for capturing a specimen was especially helpful for complete identification. This one happened to be a female as evidenced by the collection of eggs at the tip of its abdomen in the photo below.

Common Baskettail (female) with eggs

The first dragonfly at the top of this post is the 12-Spotted Skimmer. The male is different from the female mostly due to the white patches in between the black patches on each wing. Female 12-Spotted Skimmers and female Common Whitetails are very similar except for the shape of the yellow-ish markings on the two species abdomens. Perching behavior is helpful for identifying these two similar species: 12-Spotted Skimmers tend to perch horizontally in vegetation and Common Whitetails tend to perch horizontally on logs, rocks or the ground.

Next time you see a dragonfly, take a closer look. You may notice the next one doesn't actually look the same as the last one. There are many species in our area and all are unique and beautiful if we take a moment to look a little closer

-Adam Zorn, Naturalist

Monday, June 15, 2009

Summer Bird Count

This past weekend, Westmoreland Sanctuary staff participated in the annual Stamford/Greenwich Summer Bird Count. For those who are not familiar, the summer bird count is conducted within a "count circle" centered near Stamford and Greenwich, CT. Westmoreland and many other local parks and nature sanctuaries fall just inside the NW edge of the count circle. In fact, a number of lower Westchester's parks and preserves land with the 15-mile radius extending from the center of the count area. Click this link to see a map of the count area.

The count is conducted by numerous volunteers from all over the area. People from all walks of life spend as much of their weekend traveling through their designated portions of the count circle searching for, identifying and counting as many species and individual birds as possible. It often leads to a lot of exercise, little sleep, and some exhaustion, but we all do it because its fun. And its all about the birds!

The Summer Bird Count is an important annual event that provides a snapshot of the species of birds that are living in, and presumably breeding in, our area each year. Year after year these snapshots provide invaluable data on the presence and status of breeding birds in our area. Every year this data becomes more important, as many of our once common bird species continue to decline in abundance all over the continent. This count is a very important way for researchers to learn about the location of breeding birds in our area.

Counting at Westmoreland began around 7am Saturday morning. Conditions were fair, but less than optimal during the day due to the clouds and on-and-off rain showers in the afternoon. Nevertheless, a total of 6.5 miles of trail was walked over a period of about 6 hours and 15 minutes. By the end of the afternoon, a total of 407 individual birds covering 46 species were accounted for on the sanctuary. This is by no means an absolute count of every bird or species on the sanctuary, but it still gives an important snapshot of the species and individuals present.

Species identified on June 13:

Turkey Vulture, Wild Turkey, Mourning Dove, Black-billed Cuckoo, Ruby-throated Hummingbird, Red-bellied Woodpecker, Downy Woodpecker, Hairy Woodpecker, Northern Flicker, Pileated Woodpecker, Eastern Wood-pewee, Eastern Phoebe, Great-crested Flycatcher, Warbling Vireo, Red-eyed Vireo, Blue Jay, American Crow, Tree Swallow, Black-capped Chickadee, Tufted Titmouse, White-breasted Nuthatch, Carolina Wren, House Wren, Eastern Bluebird, Veery, Wood Thrush, American Robin, Gray Catbird, Cedar Waxwing, Yellow Warbler, Pine Warbler, Worm-eating Warbler, Ovenbird, Common Yellowthroat, Scarlet Tanager, Chipping Sparrow, Song Sparrow, Northern Cardinal, Rose-breasted Grosbeak, Red-winged Blackbird, Common Grackle, Brown-headed Cowbird, Baltimore Oriole, House Finch, American Goldfinch, House Sparrow.

Species in bold above were observed either on the nest or feeding fledglings, which are obvious signs of breeding.

For more information about common birds in decline, please visit this link to National Audubon's State of the Birds Report.

Please join us for one of our bird walks or hawkwatching programs coming up this summer and fall to see some of these species at the sanctuary. Check the calendar pages on Westmoreland's website for dates and times.

-Adam Zorn, Naturalist

Thursday, June 11, 2009

Summer Frog Chorus

It has been a while since we've mentioned anything about the amphibious wildlife here at the sanctuary. Late March and early April brought about a flurry of amphibian activity that's unrivaled at any other time of the year, but not all species were involved. As the spring days lengthen and warm, slowly giving way to summer, our area's other frogs become more active and vocal.

Warm days and humid evenings over the last few weeks have encouraged the Bullfrogs (Rana catesbeiana) and Green Frogs (Rana clamitans) to begin their breeding seasons. Nearly any pond, lake, and wetland will be full of the deep "jug-o-rum" voice of the Bullfrog and the "loose banjo string" voice of the Green Frog. Another species involved in the chorus is no less noticeable, but is far more difficult to locate.

Gray Treefrogs (Hyla versicolor) are stepping up their breeding efforts at this time of year as well. They are most vocal from late spring through early summer during the evening and night hours, but are also likely to call during warm overcast afternoons. As the name Treefrog implies, they typically inhabit forests, but are also common in neighborhoods and gardens with plenty of vegetation for hiding and foraging. Their loud, trilling voice announces their presence, but their extraordinary camouflage makes them difficult to see.

I've been hearing a couple of Gray Treefrogs calling around the museum and naturalist's cottage for the past week. One in particular always sounds very close to the cottage, but I was unable to find him for a few days. In the evening as the sun is setting and after dark with a flashlight, my search came up empty. This past weekend I finally found him near the wildlife garden beside the cottage.
Can you find the frog in the photo?

My first pass through the garden came up empty, but I knew he was in there. There's a lot of flowers and other plants in which he may have been hiding. There are a lot of spaces between the rocks around the garden's pond as well. I knew I was close because he stopped calling during my search.

After I walked away for a few minutes, he started calling again. As I approached the garden, he stopped. I knew that he had to be close to the front of the garden. I retreated again and went to grab my binoculars. The incredible camouflage of this frog's skin would make him hard to spot, but the frog's calling creates movement. Scanning carefully across the front of the garden with my binos, here is what I found:
Can you see him now?

Each time he called, his throat would swell to resonate the sound into the surrounding area. This little bit of movement was enough to locate the frog in his secret location. What a perfect place to hide. Look at the photo below to see how well this guy is capable of melting into the background of his hiding place:
Gray Treefrog (Hyla versicolor)
As their scientific name implies, this frog is capable of changing colors to match it's surroundings. Colors can vary from nearly black to nearly white with varying degrees of mottling. If you're lucky enough to find and handle a Gray Treefrog, you'll notice bright yellow patches on the underside of it's hind legs. Quite an extraordinary sight from such a well camouflaged animal.

Enjoy this summer's frog chorus and keep an eye out for the froglets of various species emerging from our local ponds and wetlands.

-Adam Zorn, Naturalist