A Gnatcatcher s Strategy, 



41 



contained five eggs, taken on the 2d of 

 last May, was but 5^ inches in circumfer- 

 ence by 2^ inches in length, and weighed 

 only 3.7 grams. But the cowbird cares 

 nothing for the size or form of the chosen 

 asylum for her young. If it is only large 

 enough for one t.g<g, it is sufficient for her 

 wants, and she forthwith appropriates it to 

 her use without even a "by your leave " to 

 the rightful owners. And so, very often, 

 among four or five delicate little gnatcatch- 

 ers, there is found a large chuffy youngster, 

 whose demand for food is incessant, and if 

 supplied in sufficient quantity, he will in a 

 day or two fill the entire nest, and smother 

 beneath his greater bulk the lives of the 

 lawful occupants. It is one of those numer- 

 ous cases of a struggle for existence in 

 which the most overbearing, ugliest, and 

 strongest survives, instead of the fittest. 



However, I suppose that the modern evo- 

 lutionist would say, that in this case ugli- 

 ness and brute strength are necessary quali- 

 ties of the "fittest," and that nature has 

 ordained that the cowbirds shall increase 

 in numbers as the "Jay Goulds" of to-day 

 grow in wealth, only at the expense of their 

 weaker brethren. 



But one — or rather two — cowbirds' eggs 

 laid last season did not hatch, and it was of 

 them that I started to write. On the 2 2d 

 of April, while out for a walk, I discovered 

 a pair of gnatcatchers building in a maple 

 tree about thirty feet from the ground. A 

 week later on passing near the spot, I saw 

 that the nest had assumed massive pro- 

 portions for one of that species, and on 

 climbing up to investigate, found that it con- 

 tained a single cowbird's fgg. The owners, 

 however, had not deserted it, for they soon 

 appeared, circling rapidly around, and ut- 

 tering their shrill cries of distress. I left 

 them immediately, merely supposing that 

 they were young birds, not fully up to the 



times in nest building, and therefore had 

 formed a large, loosely-constructed nest, in- 

 stead of a small compact one, as is usually 

 the case. 



On the 5th of May I again visited the 

 tree, and found that the birds had aban- 

 doned the nest without laying in it, and were 

 building a new one in the top of a tall oak 

 a short distance away. Removing the old 

 nest carefully I carried it home in order to 

 compare more closely its size with the one 

 taken a few days before. Judge of my sur- 

 prise when, on examining it thoroughly, I 

 found that it was a double nest, or rather a 

 "two-story" one. The lower part, or first 

 floor, was neatly and closely built, and in it 

 was found a second cowbird's egg. It had 

 evidently been laid shortly before the nest 

 had reached the usual size of such struc- 

 tures, and the builders, on discovering it, 

 had immediately set to work and covered it 

 entirely over, and then built up the sides of 

 their house about 2}4 inches higher. But, 

 alas, for the expectations of our feathered 

 friends ! No sooner had the second floor 

 neared completion than Mrs. Cowbird paid 

 them another visit, and left behind her a 

 reminder in the shape of a new &gg. It was 

 too much for bird endurance. They de- 

 serted in disgust the home over which they 

 had spent so many anxious moments, and 

 set to work to build a new one, in which, 

 let us hope, they reared their little family 

 unmolested by unwelcome guests. On 

 measuring carefully the double nest I found 

 its .circumference to be 9^4 inches; its 

 length, 4^ inches; and its weight 12 grams, 

 or about ^y'i times that of the one first 

 taken. The upper 2^ inches was very 

 loosely constructed, and had evidently been 

 built in a hurry to meet the exigencies 

 of the case. The new nest in the oak was 

 too high for close observation, but seemed 

 from the ground to be only of normal size. 



W. S. Blatchley. 



