INTRODUCTION xxxi 



of the back, if the bird is a male, you will see the two oval, usually 

 light colored testes, in the breeding season large and conspicuous, 

 at other seasons small, and, in immature specimens, often difficult to 

 find. If the bird is a female, in place of the two oval bodies there 

 will be the ovary, a mass of spherical ovules, large or small ac- 

 cording to the season, and often obscure in immature specimens. 

 The male sign is Mars' arrow ( ), the female, Venus' mirror (9). 



Collecting and preserving eggs. Egg collecting is justifiable only 

 when the collector's earnestness of purpose warrants the sacrifice of 

 happy bird homes, and no amount of pains and care should be 

 spared to make each set a permanent and valuable illustration of 

 the life history of the species. So far as possible only complete 

 sets of fresh eggs should be taken. An incomplete set is of sec- 

 ondary importance, and eggs in which incubation is advanced are 

 not worth troubling with unless very rare. 



The first step is to identify the nest positively, which, in cases of 

 rare species, can often be done only by collecting one or both of the 

 birds. Eggs are worse than worthless if there is any question of 

 their identity. 



The next step should be to photograph the nest from at least two 

 points, one to show general setting and one at closer range to give 

 detail of form and structure. Then notes should be made on the 

 position, structure, and materials of the nest, the actions of the old 

 birds, and the manner of identification, etc. When possible the 

 nest should also be collected. 



Each egg should be wrapped in cotton and each set packed snugly 

 in a wooden box with plenty of cotton for carrying home. 



The tools necessary for blowing eggs are a slender blowpipe and 

 two drills, large and small, which can be bought of any dealer in 

 naturalist's supplies. 



For drilling, hold the egg lightly between the thumb and two 

 fingers of the left hand, and placing the sharp point of the drill 

 against the side twirl it evenly with a slight pressure until it sinks 

 into the shell, grinding out a smooth round hole which points down- 

 ward, from the size of a pin-head in a fresh sparrow's egg to an 

 eighth of an inch in diameter in a larger or partly incubated egg. 

 In much incubated eggs it is often necessary to make a much larger 

 opening. A fine stream of air should be forced into the egg without 

 touching the blowpipe to the opening, and the contents gently forced 

 out. When the shell is empty, with mouth full of water blow a 

 stream into it and rinse out thoroughly, afterwards blowing all the 

 water out and laying carefully away to dry. 



