LIFE HISTORIES OF NORTH AMERICAN WILD FOWL 275 



The fulvous tree duck is a common species in some localities along the Rio 

 Grande River. In the hreediug season the birds are frequently seen singly, 

 perched in large trees in the heavily timbered bottom lands. 



I secured two sets of their eggs, one of which contained 14 and the other 11 

 eggs. Both of these nests were found by Mexicans, and one of them I visited 

 and examined. This nest was a natural cavity in the large trunk of a mes- 

 quite tree and about 4 feet from the ground ; the cavity was about 2 feet in 

 depth and the eggs, 11 in number, were placed on rotten chips at the bottom. 



The eggs are deposited at a warm time of the year, and I am informed by 

 the Mexicans that the birds are in the habit of leaving the nests for the 

 greater part of the day, the heat of the sun continuing their incubation, but 

 they return and remain upon the nest during the night and the cool part of the 

 morning. How true this is I am not able to say, as I had no opportunity of 

 watching them, but it seems quite reasonable. The nest was more than half 

 a mile from the Rio Grande River, in a broad mesquite bottom. 



Eggs. — Either the fulvous tree duck lays an extraordinary num- 

 ber of eggs or several females lay in the same nest. Mr. Shields 

 (1899) says: 



We subsequently found about a dozen nests, all similarly situated, and most 

 of them containing from 17 to 28, 30, 31, and 32 eggs. The smallest set found 

 was of 9 and another of 11 eggs, both evidently being incomplete, as the nests 

 were not finished and incubation had not commenced. 



Authentic sets of as many as 36 eggs are in existence and probably 

 much larger numbers have been found according to F. S. Barnhart 

 (1901), who writes: 



From time to time since 1895 pothunters have told wonderful stories of find- 

 ing large numbers of eggs piled up on bunches of dead grass and on small knolls 

 that rose above the water in the swamps. The number of eggs in these nests 

 ranged from 30 to 100 or more, according to report, and in not a few cases the 

 finder has brought the eggs with him in order to prove that what ho said was 

 true. 



Probably the large numbers referred to by Mr. Barnhart are 

 surplus eggs laid by various individuals and never incubated ; and 

 perhaps some of the large sets in collections are the product of more 

 than one female. Evidentl}^ the fulvous tree duck is careless in its 

 laying habits, for Mr. Shields (1899) speaks of finding eggs of this 

 species in the nests of the redhead and the ruddy duck. All of the 

 slough-nesting ducks seem to be careless about laying in each other's 

 nests and to have the habit of using "dumping nests" i-n which 

 large numbers of eggs arc laid and forgotten. 



In shape the eggs are bluntly ovate, short ovate, or oval. The 

 shell is usually .smooth and without gloss, but in many specimens, 

 probably those that have been incubated, the shell is quite glos.sy 

 and minutely pitted. The color varies from white to buffy white, 

 but the eggs are often much stained with deep shades of buff. The 

 measurements of 212 eggs, in various collections, average 53.4 by 40.7 

 millimeters; the eggs showing the four extremes measure 59.9 by 

 40.4, 52.5 by 44.03, 49.1 by 39.7 and 51.7 by 37.6 millimeters. 



