Birds

Great cormorants: Photo By E. Vernon Laux
Great cormorants. This species, the European or great cormorant, is the one that is commonly seen during the winter months. Their numbers have remained steady, unlike the exponential increase in the numbers of double-crested cormorants.

Summer solstice

Story & Photo By E. Vernon Laux - June 22, 2006

The month of June always surprises and startles. After the exciting migration of May with nocturnal waves or pulses of birds passing by in the night sky, some returning to the Island to breed, others bound for points further north, and the great numbers of sea birds moving along shorelines, it is surprising at how quickly the migration ends.

It seems prudent to pause for a moment to ponder the passage of the planet as it reaches the summer solstice. The earth's annual, predictable rotation around the sun is an endlessly fascinating topic that never ceases to amaze even the casual observer. This is a hugely important event for all living things on this planet, and birds are tuned in to differing seasonality and are able to take advantage of it more than any other life forms.

The earth has just past its maximum tilt towards our powerful star and begun spinning back to a different plane. What this means is that in the northern hemisphere, the longest day, the maximum hours of light, has come and gone, with the official start of summer occurring yesterday. It means that the pendulum of time and seasons has already graced us with maximum sun and daylight and that the days are already starting to shorten and will continue to do so until Dec. 21.

In the Arctic, where many migrant species of birds are nesting, the day is different than around here. The sun just moves around the horizon at this season, never setting - in other words, it is constant daylight 24/7, hence the expression "midnight sun." There is no night for a couple of months, which makes life at the higher latitudes distinctly different than anywhere else.

Conversely, in the southern hemisphere it is the reverse, so the shortest day of the year, total dark in the Antarctic, and the coldest temperatures on earth are occurring there now. Of course on the equator there is virtually no change in season as the sun is always overhead, with 12 hours of both day and night. There the seasons are just two, rainy and dry; it is always hot. With the advent of summer it seems counterintuitive to suggest that day length is now decreasing, but that is a fact. Don't worry, be happy, enjoy the summer; Labor Day will be here soon enough.

Back on the Island, it is hard to miss the ospreys. The unofficial mascot of the Vineyard, these large, powerful fish eagles are exciting to watch. It is easy to become mesmerized watching one hunt along a shoreline. Seemingly gigantic birds, they often go into a hover, staring intently into the waters below. Often starting into a dive, and then aborting as the fish moves or visibility wanes, they come around for another pass.

The older, more experienced the osprey, the better it is at fishing. At this time of year, one encounters adults with young in the nest. Watch and keep score as they plunge towards the water, throwing their talons out at the last moment to break the impact and enter the water first, hoping to grasp some finny prey. Some birds are remarkably successful and seem to never miss, like some sort of aerial fishing ace, top gun fishermen, if you will.

Cold wet weather makes things very difficult for adult birds trying to feed nestlings. Whether the prey is fish, insects, or worms, cold and rain retard insect emergence and activity at a critical time for developing birds. Adults must provide the necessary protein to the nestlings, and this is very difficult in prolonged rainy conditions or with a persistent northeast wind blowing.

A species that is increasing and is seemingly everywhere in both fresh and salt water, the double-crested cormorant, is experiencing a booming population expansion all over this continent. Why they are doing this is hard to explain, and though there are dozens of possible reasons, there is no one answer. Most plausible is that the birds are enjoying the protection that was afforded them many years ago but never enforced. Breeding colonies are protected from disturbance by disgruntled fisherman, and the birds have responded. Some would say with a vengeance.

It may be that simple, or not. At any rate these birds were uncommon here only 20 years ago; now they nest on-Island and nearby on other islands, and they are changing the natural landscape. They fish/hunt cooperatively, forming a line and driving schools of fish against sand bars or shorelines, where they corral them and eat prodigiously. They eat from the smallest minnow to medium-sized fish.

It appears that they may be overfishing whatever they go after. It will be interesting to observe the species' status over the next 20 years. Will they continue to increase, level out, or decrease? Time will tell and there are experts predicting all three of these outcomes. The natural world is marvelous.

Until next week - keep your eyes to the sky!

To contribute news about birding activities or sightings, call The Times Birdline, 508-693-6100, extension 33, or e-mail birds@mvtimes.com.