364 BULLETIN OF THE BUREAU OF FISHERIES. 
with as little detriment as possible to the birds. Two years ago a ‘“‘closed” 
season of five months was established, to include the months of November to 
March, which constitute the height of the breeding season, and the writer was 
instructed to make a study of the habits of the birds, with reference to deter- 
mining whether such a period was proper or adequate, or whether other methods 
of regulation were required. As a result of the studies made on various visits 
to the chief rookeries, it became apparent that the closed season adopted was 
inadequate, although it was a most significant step in the right direction and 
has undoubtedly already yielded results of value. 
The pelican rookeries on the 1st of April were covered with eggs 
containing live embryos, and with all stages of young birds, immature and 
incompletely feathered. Young pelicans only partially feathered were to be 
found as late as June. Cormorants were feeding their young from mouth to 
mouth in June, while already the preliminary love plays and preparation of 
nests for the following season were in progress. By the end of July a large 
number of eggs were laid for the following season and a few even had hatched. 
It follows, therefore, incontrovertibly, that there can be no season when 
the islands may be worked without disturbance of the birds. I believe the 
rookeries of pelicans and cormorants are never deserted voluntarily except for 
so long a period in the day as may be necessary to secure food. The breeding 
season of the gannet, as has been mentioned, is continuous throughout the year. 
It becomes very clear, then, that only a very carefully and consistently 
followed plan of rotation in the working of the islands would insure the birds 
the best conditions for undisturbed breeding. For a period of at least five 
years certain islands in each region might be left as the unmolested abode of 
the birds, while the extraction of guano was being prosecuted on other islands. 
At the expiration of that period, certain other islands would be closed while 
the accumulations of guano on the previously closed islands would be avail- 
able for extraction. The system might be worked out in such a way that each 
year certain islands would be opened, and a steady supply of guano be avail- 
able each year.” 
In partial adoption of a plan of rotation, the government has kept the 
south island of the Chinchas entirely closed during the past two open seasons, 
and it is estimated that by the expiration of the third year of closure there 
will have accumulated on this one island about 20,000 tons of guano of the 
highest grade. It is only fair to state that the government has enforced the 
closed season and kept this island closed in the midst of very serious difficul- 
@ The plan which the writer drafted in 1907 for the Chincha and Ballestas Islands and other points 
of the region (Boletin del Ministerio de Fomento, Junio, 1907) may be cited as an illustration. After 
further observation of the birds on the rookeries, I would modify this plan by using five-year instead of 
three-year periods, as was then suggested. 
