30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I50 



Least grebes are especially common on the extensive backwaters 

 of Gatun Lake and the Rio Chagres above Gamboa. In Bocas del 

 Toro many frequent artificial ponds made in connection with the 

 banana farms around Changuinola. It is probable that they have 

 increased in number in recent years because of the greater extent of 

 suitable habitat, formed by dams, now available. On large expanses 

 of water least grebes may congregate in groups of a dozen or may 

 remain in scattered pairs. It is common to find them on smaller pools 

 of 50 to 100 meters in extent, where usually they remain in the 

 cover of aquatic vegetation. They seem to fly about to a considerable 

 extent, as I have seen them appear overnight on small ponds in 

 mountain areas several miles distant from larger lakes. 



They present an attractive appearance as they swim with head 

 and neck erect, rest in the sun to preen, often rolHng far over 

 on the side to reach the breast feathers, or dive alertly in feeding. 

 When approached in a boat they may rise in flight and with wings 

 beating quickly, gather momentum by pattering the feet on the 

 water, and then, when fully under way, fly with neck and feet 

 outstretched. Such flights, barely above the water surface, are of 

 short duration, and usually when the bird alights it dives. 



In nesting they arrange a rounded mass of plant materials, 

 anchored to twigs of a submerged tree or amid aquatic vegetation, 

 with the top from 30 to 60 centimeters across, elevated sufficiently 

 so that the eggs, placed in a slight depression in the center, are a 

 few centimeters above the water. Such nest structures may be 

 concealed, or in larger water bodies may be visible for some distance. 

 The nesting season appears to be irregular, for I found half-grown 

 young on Isla Coiba January 14 (1956), eggs at Changuinola March 

 4 (1958), and fully grown immature birds at Pedasi March 17 

 (1957). Eisenmann (Condor, 1957, p. 249) records them as breeding 

 in June and July near El Volcan. Information available, mainly from 

 the northern end of the range of this subspecies, indicates that the 

 eggs number 3 to 6 in a set and measure 30 to 38 mm. long by 22 

 to 25 mm. broad (Bent, U. S. Nat. Mus. Bull. 107, 1919, p. 37). 

 They are dull white in color when laid but become stained im- 

 mediately to a deep buff from the wet material with which the parent 

 covers them whenever it leaves the nest. One incubating bird that 

 I shot in this act at Changuinola was a male. 



Zimmerman (Auk, 1957, p. 390) has recorded what appeared to 

 be courtship display in these grebes seen at the end of April on a 

 forest pond in Campeche. Two birds (apparently male and female, 



