NORTH AMERICAN MARSH BIRDS 203 



Eggs. — This night heron usually lays from three to five eggs, some- 

 times only two or even one, occasionally six and very rarely seven 

 or even eight; the larger sets may be the product of two birds. In 

 shape they vary from ovate or oval to cylindrical ovate. The shell 

 is smooth with no gloss. The color is pale bluish green, varying 

 from "glaucous green" to "pale fluorite green." The measurements 

 of 48 eggs average 51.5 by 37 millimeters; the eggs showing the four 

 extremes measure 68 by 35.5, 50 by 39.6, 48 by 36.6 millimeters. 



Young. — Doctor Gross (1923) found that the period of incubation 

 varied from 24 to 26 days and that both sexes take an active part in 

 it; he "frequently had nests under observation when the shift from 

 one sex to the other took place. Sometimes the shift involved a 

 domestic quarrel in which there resulted a vigorous interchange of 

 sharp, rebuffing shrieks accompanied by violent thrusts." He says 

 it is customary to start incubation after the first egg is laid, although 

 it may take a week to complete the set; this accounts for the in- 

 equality in the sizes of the young. He describes the hatching 

 process in detail; a young bird which had pipped the shell at noon 

 was not entirely free from it until 4.20 p. m. the next day. 



Young night herons are fed by their parents until they are large 

 enough to learn to fly and fish for themselves. Doctor Gross (1923) 

 says: 



The first food received by the downy young consist of juices of predigested 

 material. In the examination made at Sandy Neck, this food was so completely 

 liquified that it was practically impossible to determine the kind of animals com- 

 posing it. In delivering the food to the downy young the adult seemed to insert 

 the tip of her beak into the wide open mouth and the transference of the juices 

 was made with comparatively little effort. The parent bird usually delivers 

 small amounts at rather short intervals and I have frequently seen, from my 

 blind, the downy heads of day old birds appear between the feathers of the par- 

 ent to receive their ration of fish extract. By the third day, more substantial 

 food, such as semidigested fish and shrimp, were given to the young. Among 20 

 regurgitations of nestlings 3 to 10 days old 16 were made up entirely or largely of 

 shrimps present in pieces ranging from a few millimeters to one and in some 

 instances three centimeters in length. When the young became more than three 

 weeks old the food was made up chiefly of fish, which were often delivered with- 

 out any predigestion. 



I have several times watched the old birds feeding their young; the 

 method varies with the ages of the young. The old bird approaches 

 cautiously, climbing over the branches towards the nest and giving 

 a few warning calls, soft guttural croaks, at which the young rise up 

 in eager anticipation, or, if they are large enough, scramble over the 

 branches toward her; she may keep them waiting for several min- 

 utes, but, when ready to feed them, she raises her crest, fluffs out 

 her plumage, half spreads her wings and lowers her head to regurgitate 

 the food. If the young are small, she inserts her bill into the mouth of 



