5S 
THE CONDOR 
Vol. XIII 
construction of numerous large storage reservoirs, with the consequent seepage and 
marsh land, suitable breeding grounds have increased in number many fold; and in 
the case of the Barr Lake region at least, these birds are now common summer resi- 
dents and breeders, and so far as my own observations go I should say that a fair 
proportion of migrants make this the terminus of their northward migration. 
The first appearance of the terns in the spring was about May first; our earliest 
record was April 27, 1907, on which date a total of fifteen birds w'as noted, at dif- 
ferent points along the Barr chain of lakes. We did not note any extensive migra- 
tion of these birds immediately following this date, and in fact we did not see any 
migrating flocks of terns which w'e did not have good reason to believe were a part 
of the local breeding colony. However, northward moving flocks might easily have 
passed through between our weekly visits to the lakes, or during the night. 
By May 10, or a few days later, the full quota of breeding birds had apparently 
arrived, and nest building was begun within a few days. May 11, 1907, the nest- 
ing sites had apparently been selected, as the birds made a great commotion when 
we visited the spot, and the first egg was found May 17. 
Fig. 2-4. THE INJURED FORSTER TERN .4ND NEST 
The nesting site was a large musk-rat “house”, standing in the dense cat-tail 
swamp surrounding a small rush-bound lake. The house which stood in about two 
feet of water, projected about two feet above the water, and the eggs were laid in 
a slight cavity among the dry cat-tail stalks composing the house. These nests 
corresponded exactly in location and construction with those we had examined the 
preceding year. On this date (June 9, 1906) we examined fifteen nests, all located 
on musk-rat houses, and containing eggs exhibiting all stages of incubation. The 
fifteen nests contained one set of six, two sets of five, nine sets of three, and one 
nest a single egg. 
On May 24, 1907, (a week after the first eggs were found) the breeding colony 
was in full swing, and we were surprised to find a number of nests, containing 
complete sets, which had been built by the birds upon floating masses of decay- 
ing cat-tails. 
These structures were all made entirely of dead cat-tail stalks, and wdiile they 
varied greatly in size and bulk, the general plan of construction w'as the same in 
all, being a compact pile of material of irregular outline, apparently floating on the 
