BARRO COLORADO ISLAND—GROSS 337 
pictures of the various stages of the young it was necessary to remove 
the birds from the nest. We were unable to photograph the bird 
in the act of feeding the young; neither was it possible for us to 
study this part of their behavior. 
In the course of our life-history work with any bird the eggs are 
measured and are weighed at different periods of incubation and 
after the eggs hatch, the young are weighed, measured, and photo- 
graphed each day until the time of leaving the nest. Since such 
frequent visits might interfere with the normal growth of certain 
birds, other nests of the same species are used as controls where visits 
are made not oftener than once or twice during a week. The data 
thus obtained give us a complete record of growth and behavior 
which is of value in making comparative studies. As an example 
it was found that the incubation period of the eggs of myiobius was 
21 days, whereas the flycatchers in the temperate regions hatch in 
much less time. Even the large eggs of such representatives as the 
kingbird do not require more than 15 days’ incubation and the 
smaller flycatchers which are about the size of myiobius hatch in 
about 12 days. Furthermore the time spent by the young of this 
species in the nest was three weeks, whereas flycatchers of this size in 
the North are equipped with a plumage and ready to fly in about 
one-half of that time. Whether these conditions are general in the 
‘Tropics remains to be determined by further work and it is yet 
too early to advance a theory to account for this striking difference 
in the flycatchers. Another fact, which has been noted by others 
but emphasized by our observations, is that in general birds in the 
Tropics lay fewer eggs than the birds in the temperate regions. 
With very few exceptions there were not more than two eggs in the 
nests we found in Panama, whereas representative species of the 
same families in the North lay four or more eggs. The purple gal- 
linule (Jonornis martinicus) which usually lays as many as eight 
eggs in the North, did not have more than three or four eggs in the 
nests which we studied in the Canal Zone. 
On August 4, Donato, the Indian boy, showed us a nest of the 
piliated tinamou (Crypturus soui panamensis), a fine game bird 
of the Tropics, located at the base of a palm tree on the Snyder- 
Molino trail. We approached cautiously and took several pictures 
of the bird on the nest at close range without the use of a blind. 
We then went nearer until I was able to touch the feathers of the 
bird. She did not move and when I persisted she picked at my 
fingers. Finally I reached under her breast to feel for the eggs, but 
this proved too much of an intrusion and she left the nest, walking 
leisurely into the dense undergrowth a few yards away. The two 
eggs were of a vinaceous brown, very different from the colors we 
