4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



time during the Pleistocene, it is apparent that then the island was 

 part of the mainland. A similar connection should have come during 

 part or all of the three preceding periods of maximum glacial ice. 

 Return of warmer temperatures in the interglacial periods, which 

 melted the ice, again raised the water level, placing Escudo once more 

 as an island, remote at sea. It is reasonable to suppose that the resi- 

 dent wren and the manakin, as well as the peculiar spiny rat of the 

 island, were established there during one of the periods of land con- 

 nection, since they are jungle creatures that do not range far from 

 cover, nor are the birds of kinds that would be readily windblown 

 by violent storms. Whether the characters of size and color that now 

 mark them were theirs in whole or in part on their arrival, or whether 

 these are distinctions that have developed during isolation, cannot 

 be said, except that it seems probable that the peculiarity of greater 

 size may have become intensified, since this condition is found regu- 

 larly in populations that seem to have been restricted for long periods 

 to small islands. The manner of development of the differences that 

 mark the blue-gray tanager is not easily understood since in mainland 

 regions these birds appear to roam far. It would appear that they may 

 not cross fairly wide water barriers, since another insular form is 

 found on Isla Coiba off the Pacific coast of Panama (Wetmore, 1957, 

 p. 94). 



Though there were few species of resident birds on Escudo de 

 Veraguas, individuals were fairly numerous. The songs of the bay 

 wren, joined occasionally by the raucous notes of a small flock of 

 parrots, were regular bird notes of the jungle, aside from which there 

 were only the subdued sounds of the wind in the higher treetops, and 

 of the wash of waves against the shoreline. The smaller birds were 

 encountered mainly in the more level areas, where at times they were 

 detected with difficulty in the dim shadows that prevailed in the 

 thickets when the sky was overcast. Occasionally I noted large spiny 

 rats of the genus Hoplomys. One that I shot on the ground proves 

 to be a form new to science. 



ANNOTATED LIST 



Family Pelecanidae : Pelicans 



PELECANUS OCCIDENTALIS Linnaeus: Brown Pelican, Alcatraz 



Pelecanus occidentalis Linnaeus, Systema naturae, ed. 12, vol. 1, 1766, p. 215. 

 (Jamaica.) 



Several were fishing around the island on the morning of March 2. 



