ANDERSON — THR BIRDS OF IOWA. I 59 



County records: Lee — "I find I have never seen it, but speci- 

 mens locally obtained are in local collections, with no data. Cur- 

 rier has seen them on Jime 20, 1888, on bars of Des Moines, act- 

 ing as if they were nesting" (Praeger). Linn — "rare migrant" 

 (Berry). Polk — "rare" (Johnson). Pottawattamie — "scarce 

 migrant" (Trostler). Sioux — "rare" (Johnson). Winnebago — . 

 "several seen in company' with Black Terns at Rice Lake, June i, 

 1895; one shot" (Anderson). 



Genus HvDKOCHjajDON Boie. 



21. (77). HydrochcUdoii nigra surinamciisis {QjW\<A.). Black Tern. 



The Black Tern, usuall}" known in Iowa as the "Slough Gull," 

 is an abundant migrant over all sections of the state, nesting 

 commonly in suitable localities in the northern half of the state. 

 The writer has observed only a few specimens in Johnson county, in 

 the month of May, but in Winnebago and Hancock has observed 

 them abundantl)^ from the early part of May until September. In 

 early .spring hundreds may sometimes be seen at one time, and if 

 one is shot the others will hover over their fallen comrade in the 

 water. Later in the season thej' are not generally seen in such 

 large flocks, being scattered around in different sloughs, nesting. 

 In some sloughs only one pair ma}^ be found, while others have 

 from ten to fifty pairs. The Black Tern seems to prefer grassy 

 and reedy marshes, in which the nest, an almost flat mass of 

 grass, reeds, moss and mud is placed, raised a little above the 

 surface of the water, and often floating. The eggs are two or 

 three in number, varying remarkably in size, shape, and colora- 

 tion, no two sets being alike; but all eggs from the same set have 

 a close similarity. In this locality the Black Tern rears two 

 broods in a season, the first set being deposited in the latter part 

 of May or first of June, and the second set in July. In only one 

 instance have I found a nest that was not placed over water — 

 this was simply a few weeds arranged in a circular form on a piece 

 of low ground quite a little distance from the water. 



Dr. J. A. Allen records "great numbers, July 20, al)out Wall 

 Lake, in Sac county. The young had already flown and were 

 accompanying the parents" (Mem. Bost. Soc, i, 1868, 502). In 

 Decatur and Mahaska, T. M. Trippe observed them "about pools 

 of water on the prairies in May only" (Proc. Bost. Soc, xv, 1872, 



