A Comparitive Study at Cobb's Island, Va.
On June 22, 1909, I arrived at Cobb's Island, Virginia, equipped for a week's stay, having made the trip solely for the purpose of ascertaining the conditions then prevailing among the water birds breeding there, in order to compare them with the facts gathered by Mr. T. Gilbert Pearson in 1892 (Oologist, Vol. IX, No. 8) and Mr. Frank M. Chapman in 1902 (Camps and Cruises of an Ornithologist) in the same locality. I chose this island in preference to others because it is uniformly well known.
There is frequently a change from year to year in the prevalent conditions among a colony of birds, until at the end of a decade, it has often become very pronounced. Sometimes these changes can be ascribed to known causes, and again the reasons are veiled in mystery even to the most observant.
In the good old days Royal and Least Terns bred upon the
island by the thousands, but they have been driven away and neither of them has bred in the locality for years. Willet also were extremely abundant at one time, but this cannot be said of them at present. Following is a list of breeding water birds found upon the island at the three different periods referred to. Mr. Pearson in his paper, failed to give the approximate numbers of birds observed of some of the species, and therefore I am compelled to estimate from the general trend of the article.
Mr. Pearson, 1892 | Mr. Chapman, 1902 | A. B. Howell, 1909 | |
Laughing Gull, Larus atricilla | common | several hundred | 2000 |
Gull-billed Tern, Gelochelidon nilotica | mere mention | 16 | 16 |
Forster's Tern, Sterna forsteri | considerable number | small number | 0 |
Common Tern, Sterna hirundo | considerable number | several hundred | 300 |
Black Skimmer, Rynchops nigra | large number | thousands | 300 |
Willet, Catoptrophorus semi-palmatus | 10 | 2 | 4 |
Wilson's Plover, Ochthodromus wilsonius | not uncommon | 2 | o |
Oyster-catcher, Haematopus ostralegus | several pairs | 2 | o |
The stories which I heard concerning the wholesale slaughter of Sterna antillarum in past years are almost beyond belief. For ten cents apiece, men shot these birds until their shoulders had become too raw to fire a gun; shot them by the hundreds and the thousands as long as there were enough left to pay for a morning stroll. Small wonder that they have been wiped out entirely in this locality. The scarcity of the Willet, Oyster-catchers and Wilson's Plovers can be ascribed to the depredations of visiting sportsmen. I searched in the marshes for Forster's Terns, but in vain, for although I caught a glimpse of what may have been one of these birds, I cannot be sure. The Gull-billed Terns seem to be holding their own, as do the Common Terns, which latter are apt to be found nesting anywhere along high water marks, but seem to prefer the colonies of Skimmers.
The most interesting problem was the reason for the rate of increase and decrease in the numbers respectively of the Laughing Gulls and Black Skimmers. The latter were nesting in four rather small colonies several miles from the Life-saving Station, and as they nest later than, and their eggs are smaller than those of the Gulls, the fishermen confine their attention almost exclusively to the nests of the latter. More than this, the people of this section have a more kindly feeling towards the Skimmers than the Gulls, and the plumage of the former has always been of even less value commercially than that of the latter. The nests of the Laughing Gulls are robbed by the fishermen twice, so I am told, and at the third setting of eggs, are left in peace, but one would think that even with this slight encouragement, they would leave the island for more favorable localities. However, they are thriving and growing fat and increasing from year to year, while the sea dogs, as the Skimmers are called locally, seem destined to take the trail back to the Southland. Nor can their growing scarcity be due to high tides flooding their nests, for these as a rule are higher above the water than are those of the Gulls. The only explanation that seems to be left is one which Mr. E. J. Court of Washington, assures me is now accepted by the majority of ornithologists who are conversant with the conditions of that section. It is that the schools of a certain small fish on which the Skimmers feed almost exclusively, have within the past few years forsaken the locality, and that now there are only enough left for the few birds remaining. Another reason that some have advanced is that during a series of heavy winter storms several years ago, the southern end of the island was washed away. However, as fully nine tenths of the original island is left, this supposition seems to be hardly worth mentioning.
Clapper Rails (Rallus crepitans) are found upon the island in the greatest abundance, and evidently have always been just as numerous. At this time, most of their eggs were pipped, and a few sets had already hatched. A habit which the Rails had was that of very often placing their nests within about three feet of those of the Gulls. I am sure that this was from no feeling of friendship, for the Gulls love to tease the Rails, and I have seen them swoop at the latter on their nests, while the victims danced
up and down in great fury at not being able to reach their tormentors. In one nest of crepitans containing eggs of the rightful owner there were two eggs of the Laughing Gull, but these had been pushed to one side. These bird's nest were very easy to find on account of the tall marsh grass being bent over them toward the center, dome-fashion.
I took an umbrella blind with me in order to facilitate my photographing, and also to study the nesting birds at close range. It is no light work to start out for a walk of six miles through the soft sand laden down with a heavy camera, several dozen plates, large umbrella tent and other paraphernalia, not forgetting the water-bottle, when the thermometer is registering one hundred and two. However, this was refreshing compared to the dreadful heat which I experienced with the sun pouring down upon my blind after I had crawled into it and closed every cranny except two small holes. Complete quiet had settled down among the birds in less than an hour.
Mr. Chapman was the first to disprove the popular fallacy that the Skimmer incubated only during the night and in cloudy weather, and I also observed that they incubate throughout the brightest days, although they are very restless, remaining on the nest but for a few minutes at a time. One would alight on the sand, waddle up to the nest and after inspecting its contents, settle down upon the eggs. Then almost invariably she would cock her eye at the sun, and finding that orb fully up to her expectations, she would give over her thoughts to serious business for a while. This species is to me at least, one of the most interesting of the sea birds. They have a certain ease of flight that is not surpassed even by the Terns, and to see one quartering the little tide creeks at dusk is enough to stir the interest of the most blase ornithologist. They often fly in straggling flocks of about a dozen individuals, and when passing, strongly remind one of a pack of hounds on the trail, as Mr. Chapman so aptly puts it, for their cry is an almost exact counterpart of the yelp of a hound.
In the middle of the day when one decides to feed, he often chooses a place where a wave has broken and is receding down the beach. Then he flies along where the water is about two inches deep, skimming with his lower mandible beneath the surface. At
such times, he hits bottom every twenty feet or so, and his head is jerked back in a most comical manner.
The Gull-billed Terns were the only birds which continued to be suspicious of my blind, and the Common Terns accepted it as a necessary evil within a half hour.
During my stay I spent in all about eleven hours in my blind within sight of many Gulls, but they seem to be less rapacious that some of their cousins, for I saw them attempt to steal eggs only once. In this locality and at this time of year the Gulls feed almost exclusively on soft-shelled crabs, which they capture with great dexterity.
Other species of birds observed on the island were:
Green Heron (Butorides virescens), one.
Osprey (Padion haliaetus carolinensis), one.
Phoebe (Sayornis phoebe), one pair breeding.
Red-winged Blackbird (Agelaius phoeniceus), several, probably breeding.
Meadowlark (Sturnella magna), one pair.
Seaside Sparrow (Passerherbulus maritimus), abundant, chiefly at the northern end of the island.
Song Sparrow (Melospiza melodia), common.
Barn Swallow (Hirundo erythrogastra), four pairs breeding.