SIRS,--May I say something on this vexed subject ? I speak of those territorial species whose young depend upon insects for food. Three sets of facts seem connected :-- (i) T h a t in a cold and wet breeding season we find infertile eggs, chicks dead in the shell, and dead chicks. (2) T h a t if the young are exposed to the atmosphere when the temperature falls to 50 0 F . they collapse quickly du...

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