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- Depositor
- Karen Dykes
- Date Uploaded
- 2021-12-08
- Date Modified
- 2021-12-08
- Fixity Check
- passed on August 08, 2024 at 14:06
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| Transcript |
- Of clutch size + the ability of birds to raise
a given number of young. From his swift
studies he is convinced that birds that lay
more than a certain # of eggs raise a reduced
number of young as a consequence. By raise
he means bring to sexual maturity. His
best data are from a swiss study of
the starling. Here it was demonstrated
that a bird laying up to 5 eggs laid [word crossed out]
brought up that number of young - survival
rate was identified. Beyond that number
survival rate [underlined] was lowered. For second
broods the number was 4 instead of 5.
He is convinced that this principle is
applicable to all passerines. + to this lays the
larger number of eggs laid by species
in the northern parts of their ranges
where food + feeding are better.
Because gallinaceous birds similarly
lay larger clutches northwards he feels
that the same principle may apply though
he cannot imagine the mechanism. On
the other hand he readily admits to the
conundrum posed by the anseriformes.
He tells me of very good wing clips in
use by the Swedes on Downy ducklings.
Oxford. Dec [December] 11/52 [1952].
Spent the day in the library of the [illegible word] lab
where, among other things I went into a
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