Ecological and Morphological Aspects of the Breeding Bird Community of Blodgett Forest, California

DOCTORATE DISSERTATION: Data on the foraging method, foraging tree species, foraging height, territory sizes and 10 morphological measurements for foliage-feeding bird species in a mixed conifer forest in the central Sierra Nevada were collected during the summers of 1978, 1979, 1980. Niche breadth and overlap were calculated for the data nad for 2 simulations: S1-random and uniform electivities of resource states, and S2-random re-arrangement of observed resource electivities. The results indicate that: 1. NBs along 3 dimensions were independent; 2. A wider niche implied a smaller territory; 3. Heavier species occupied larger territories; 4. NOs along the 4 dimensions were all dependent...5. NO patterns within the guild were significantly different from NO according to S2; 6. The distribution of territories on 2 sites indicates that the higher intrinsic diversity in site A is the result of greater territorial overlap rather than smaller territories; 7. Linear regressions between the morphological Euclidean distance and the NOs were significant and negative; 1,4, and 7, lead to the conclusion that perhaps competition within the guild is unlikely; whereas 5 indicates the opposite. The above results, coupled with results from the morphological data analysis indicate that: 8. Size does not determine the multidimensional NB, but when the NB was decomposed, different morphological characters correlate with the various NB components; 9. Variability in various morphological characters affect NB in different ways, and the niche-width variation hypothesis cannot be categorically rejected; 10. Short-tailed heavy birds, with long wings fly faster; 11. High wing-loadings and long tails characterize zig-zag flyers; 12. Migrant species are typified by long, wide and shallow bills, short wings, low wing-loadings, short mid-toes, long tarsi and heavy bodies; 13. Strictly insectivorous species have morphological characteristics that enhance foraging maneuverability (short wings, long tails, short mid-toes and long tarsi).