232 



AMERICAN FORESTRY 



A BEAUTIFUL GROUP OF THE "GHOST PLANTS" OR INDIAN- 

 PIPE FOUND IN VARIOUS LOCALITIES IN THE DISTRICT 



Fig. 7. This is one of our best-known parasitic plants, which obtains its 

 sustenance either from roots or from decomposing vegetable matter. 

 Note the Slimy Salamander in the shadow in the foreground. 



tain species will put in an appearance in undue numbers 

 for some cause or other, and that cause should be care- 

 fully investigated. An example of this was seen during 

 last winter (1919-20), when a large number of common 

 crossbills a typical northern species suddenly ap- 

 peared in certain parts of the District. It distinctly 

 pointed to what was soon realized : an unusually severe 

 winter, with much snow. Surely the crossbills made no 

 mistake in coming a little further south during the season 

 in question. 



When birds are markedly scarce during some years, 

 we may often note a corresponding increase in the num- 



bers of certain insects upon which those birds feed. A 

 certain species of butterfly suddenly appeared in undue 

 quantities possibly for the reason that the species of 

 bird that usually fed upon its larvae was was not repre- 

 sented in sufficient force to destroy it and keep it down. 

 The entire matter of the balancing of forces of this char- 

 acter may thus be studied, and the causes for the 

 equipoise, or destroying the normal equilibrium in nature, 

 as accounted for by the abundance or the reverse of cer- 

 tain animal groups, may be systematically considered. 



Opportunities to study the nests and eggs of many 

 species of birds, both water and land forms, are, to some 

 extent, fairly good in the District. Certain marsh birds 

 breed in the less frequented sections along the Potomac 

 and Anacostia rivers some species quite abundantly, as 

 Marsh Wrens, Redwings, Rails, Waders, Sandpipers and 

 others. Notwithstanding the number of times the in -Ms 

 and eggs of such forms have been described and photo- 

 graphed, good work along these lines is always both 

 desirable and acceptable. Occasionally it requires not a 

 little skill and patience to be thoroughly successful. The 

 writer well remembers the experience he passed through, 

 many years ago, when he secured, upon a sultry summer's 

 day, a photograph of the nest which a pair of Marsh 

 Wrens had built in a cat-tail swamp, where the mud was 

 knee deep in some places. It required an entire forenoon 

 to accomplish the object, which, in the end, was wholly 

 successful. When undertaking such work, it is well to 

 have a tripod with very long legs. 



If the explorer is very fortunate, he will sometimes 

 find certain birds breeding in unusual places; he should 

 then put forth his best efforts to secure the very fines' 



A FINE SPECIMEN OF THE SPINY SWIFT. WHICH IS QUITE 

 ABUNDANT IN THE DISTRICT OF COLUMBIA 



Fig. 8. It is quite harmless. Examples are met with having a length 

 of seven inches, the males being of a brilliant azure blue on the sides, 

 bordered with black. 



photographic results. An excellent example of this 

 would be to obtain a good negative, as nearly natural 

 size as possible, of, say, the nest of the Maryland 

 Yellow-throat, where the birds had selected the 



