and Laboratory Methods. 



1521 



tent, but with the window to one side. If the focal length of the lens be 6)4 

 inches, the nest mounted at the height of four feet, and the lens be 28 inches 

 from the rim of the nest, we shall get a picture with adequate setting on a 4 x 5 

 plate. 



When the nest is excavated out of wood, as in the chickadees and wood- 

 peckers, or occupies similar cavities, as in the house wrens and bluebirds, the 

 vertical branch or stump should be mounted on a pivot, so that it can be readily 

 turned at any angle with the sun. Wherever a sky background is not available, 

 it is of great advantage to use a large screen of white cloth, which should be 

 mounted at a distance of five or six feet immediately behind the nesting bough. 

 By such devices one can obtain serial pictures of birds performing their various 

 acts in and about their nests, 

 in front, back, or profile 

 views, against a clear white 

 ground. 



After birds have once 

 adopted the changed site, 

 the addition of the white or 

 dark screen or the protect- 

 ing wire net is not likely to 

 cause the least annoyance. 

 I have seen a Baltimore 

 oriole perch on the top of a 

 tall screen in one minute 

 after it was set up, and the 

 house wren come to her 

 nest almost immediately 

 after the screen had been 

 torn up by the wind and 

 carried with a crash against 

 a neighboring fence. 



Any good long-focus 

 camera with reversible back 

 will answer, the size and 

 weight being the considerations of greatest moment. Most naturalists and 

 sportsmen, who travel long distances and carry their own traps, find a camera 

 which takes a 4 x 5 plate the most convenient and economical. I have used this, 

 but for work with the tent prefer a 5 x 7 size, because it gives a larger and better 

 picture of the object sought. For work outside the tent, a reflecting camera may 

 be used. The principal requirement in either form is a long bellows. 



In photographing a moving animal at the close range of from twenty to thirty- 

 six inches, the difficulties are by no means slight, and are not lessened by the 

 use of long-focus lenses. A lens of a focal length of ten inches or more, when 

 used so close to the object, must be stopped down in order to give the necessary 

 depth, and bring every part of the object into focus. But by thus cutting off the 

 light we reduce the speed, so that the negative with an exposure of 1 /25 sec- 



.. S ( iM 111 -! h ,1. it |iiiuii\ W iiijilpn Lli iici-iiiiK(-l li\ a family of 

 Hiiusc \\ icii--. 1 lie leiiiale, wIiilIi hab ju^t fed hei hiood, is about 

 to re-enter tlie nest tor a more careful inspection. 



