with the common rush (_Juncus communis_) and small
alder trees. For three successive seasons I watched the bird life of
this meadow, and more especially the Reed-Buntings whose behaviour I was
studying at the time. In every respect the meadow was suitable for this
bird; there was an abundance of food and numberless situations in which
nests could be placed. Each year all the pairs were successful in
rearing one, if not two broods, yet the number of pairs never exceeded
five--the first year there were three; the second year five; and the
third year four. In addition to the four pairs of Reed-Buntings, there
were in the spring of 1915, six pairs of Whitethroats, one pair of
Lesser Whitethroats, four pairs of Willow-Warblers, one pair of
Sedge-Warblers, two pairs of Grasshopper-Warblers, one pair of
Chiffchaffs, three pairs of Hedge-Sparrows, two pairs of Tree-Pipits,
one pair of Skylarks, one pair of Whinchats, one pair of Flycatchers,
two pairs of Song-Thrushes, one pair of Blackbirds, one pair of
Redstarts, three pairs of Chaffinches, and one pair of Wrens--in all,
thirty-five pairs, whose young were mainly dependent for their living
upon the insect life of that meadow and the ground immediately
surrounding it. If we allow three young to each pair--and this would
take no account of second broods--we arrive at the following result,
namely, that one hundred and five young and seventy adults had to be
supplied with food from that locality, which would mean, if the search
for food were strictly limited to that meadow, that 83 square yards
would be allotted to each individual.

Suppose now that the four male Reed-Buntings had each admitted one other
male, and that they had secured mates, what would have been the effect
upon the whole community? The four additional pairs with their young
would have represented twenty individuals, which would have represented
a decrease of 8.5 square yards in the space allotted to each individual.
The pressure of the bird population upon the means of support would then
have been materially increased; and not only the Buntings, but the
Warblers, Pipits, and all the rest would have suffered. But the result
would have been the same if, instead of the four additional male
Reed-Buntings, four males of other kinds had been allowed to enter the
marsh, and we can multiply the number four until we arrive at a point
when the means of subsistence would no longer have been adequate for the
adults, still