It is immediately apparent that Cape May and bay-breasted, the species which capitalize upon the periodic spruce budworm outbreaks, have considerably larger clutches than the other species, as Darwin would have predicted. It is of interest
that the only other warbler regularly laying such large clutches is the Tennessee warbler (V ermivora peregrina) which is the other species regularly fluctuating with the budworms (Kendeigh 1947). Thus it seems that Darwin's statement
provides an appropriate explanation for the larger clutches. It is also interesting that the standard deviation of the Cape May and bay-breasted warblers' clutch sizes is greater. This suggests a certain plasticity which can be verified, for the bay-breasted at least, as follows. If the time of the budworm outbreak in New Brunswick is taken as 1911-1920 (Swaine and and Craighead 1924) and other years from 1903 until 1938 are called non-budworm 'years, the bay-breasted warbler clutches from ,'northeastern New Brunswick can be summarized as follows: