XOTES ON GUATEMALAN BIRDS WETM'O'RE 529 



On November 10 I went out again in the forenoon and by noon had 

 two more pairs, making six in all, with which I was content. Four 

 were prepared as skins and two as skeletons. These large grebes 

 seemed rather solitary and ranged alone. At a distance they were 

 easily separated from the other species found here by much greater 

 size, which marked them at a glance. When approached they dived 

 and on appearing again showed only the head and the upper back. 

 Sometimes they swam submerged into the open lake, where they were 

 hidden by the waves and sometimes they retreated to the scanty 

 cover of the rushes along the shore. While very quick it was my 

 impression that they were slower than the common pied-billed grebe ; 

 they were certainly much slower in submerging than their small com- 

 panions, Colymhus doTninicus hrachypterus. The breeding season was 

 near in the birds taken, though one female (prepared as a skeleton) 

 was molting the wing feathers. They were not heard to call. 



At the hotel one came regularly into a tiny bay where I could 

 watch it easily. At a distance the bill appears completely white, 

 and the body dark except on the posterior portion. Wlien the 

 feathers were puffed out to catch the sun the bird appeared very 

 large indeed. Griscom's estimate of 100 pairs for the lake in 1930 

 seemg reasonably accurate for the condition that I found in 1936. 

 On November 9 I actually saw 8 birds and on November 10 between 

 12 and 15. My observations covered only a small part of the lake, 

 and I did not go out on the water except on these two days. 



Measurements of the four grebes preserved as skins are as fol- 

 lows : 2 males, wing 131.4, 139.8, culmen from base 26.0, 27.5, depth 

 of bill at base 18.0, 18.5, tarsus 48.5, 50, middle toe with claw, 70, 70 

 mm. ; 2 females, wing 122.8, 126, culmen from base 22.3, 22.4, depth 

 of bill at base 15, 15, tarsus 41.4, 42.1, middle toe with claw 61.3, 63 

 mm. 



The larger bulk of these birds as compared with the largest indi- 

 viduals of PodiJymhus podwej)s has already been noticed, the dif- 

 ference being strongly marked in the skeleton. The larger skull of 

 gigas also has stronger muscle attachments and processes, the ptery- 

 goid and the postorbital process especially being heavier. The 

 humerus in gig as is only slightly longer and very little heavier than 

 in the largest podiceps, and the crista superior, while larger, is very 

 little longer, indicating a relatively weaker wing. The distal end of 

 the humerus has the trochlea swung at a somewhat different angle in 

 gigas. 



There is no question that PodUymhus gigas is a distinct species. 



