their feeding habits, render incalculable aid to agriculture, horticulture, 
and forestry. 
The greatest value of birds. in the role of insect destroyers lies in 
the coordination of their feeding activities with all other natural factors 
of the environment in preventing the defelopment to plague proportions of 
destructive insect eruptions. Birds aid in maintaining an equilibrium in 
the biotic complex. Their repressive influence is constantly exerted, and 
their great mobility and propensity to wan nder” céuses them to Soncenbedte 
“at the sceené of any local outbreak, Frédue ogtly, they not only control a 
pest, but almost effect its local extirpa vbion, ‘Thus they. jevel off the 
waves of inséct abuhdancée aiid tend to maintain unifermity in numbers. W. L. 
McAtee: 2/ has given many examples of the’ éPfectiveness of birds Boy the con- 
trol or : suppression of insect outbreaks and has pointed out that, realizing 
this, entomologists had much to do with the establishment of ene 
Semenoiees in this country “and have constantly maintained their interest in if 
Although ‘birds often exert an importeant-degree of control on insects 
aver an extensive area, it is-usually only in very limited sections that 
they actually suppress them. In widespread invasions, for example, the 
grasshopper plagues of recent years in the Central and “lestern Stetes, birds, 
and other predatory. agents, are not sufficiently numerous to exert any 
noticeable control... Under these comet lone other factors, as unfavorable 
climate, fungus and other disease S, or artificial control (Poisons), must 
be relied upon. . 
As. a control agency.,..birds, of course, are not oT ChreCtavies as 
they do not. .kill all the pests, but the same is true of ¢ very other con- 
trol measure, biological.or artificial... It has been stated that because 
of the great fecundity of insects in comparison with thet of birds, the 
work of the latter cannot. be very effective. .Excursions into the realm of 
mathematics to demonstrate the inestimable number of progeny that may be 
produced from a single pair of. insects.profit little, as a continued un- 
checked increase. never-occurs. Those resorting to mathematical arguments 
fail to recognize the importance of the various insect predators, including 
birds, working in conjunction with all other natural and envirommental fac- 
tors when insects are present in normal numbers. . Birds have a high rete of 
metebolism, .which gives. them a most impressive consuming capacity. .A bird 
may destroy more insects. at a single feeding than individuel parasites 
destroy in a lifetime. Furthormore, birds continue to feed during seasons 
when unfavorable temperetures render insect parasites of little or no value 
as control agents. : 
The sea gull-cricket episode in Salt Lake Valley.in 1848, which saved 
the lives of the early Mormon pioneers, is perhaps one of the best-known 
instances of effective.control by. birds of a.seriousS insect pests im, Jeb5 
a similar- but less serious. and less conspicuous incident occurred in the 
same valley when another. cricket plague developed, which was again sup- 
pressed by the Californie gull early enough .in the.summer to permit a second 
. 2/ McAtee, .L.- Local suppression of. agricultural pests by birds. 
Smithsn. Inst. Ann. Rpt. 1920; 411-438, 1922, The role of vertebrates in 
the control of. insect pests. ‘smighsas Inst. Ann.. Rot. 1925; 415-437, 1926. 
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