Biometric variation among two Mangrove Warbler Setophaga petechia populations of Northwestern Mexico

Mangrove forests are one of the most productive ecosystems in the world. Despite this, over half of the world\u27s mangroves have been lost, primarily due to anthropogenic activities. Northwestern Mexico is the northernmost range of mangroves in the eastern Pacific and western hemisphere. Mangrove Warblers (Setophaga petechia castaneiceps and S. p. rhizophorae ), are small, tropical songbirds, endemic to these mangroves and are presumed to have sedentary lifestyles. Little is known about Mangrove Warblers across their range including basic life history data. Declining habitat across Mexico may be putting these populations at great risk. My primary objectives were to 1) define the biometric differences between and within the subspecies S. p. castaneiceps and S. p. rhizophorae and 2) determine local movement of a presumed sedentary mangrove bird.;In 2010-2011, I used playback and mist nets to capture, individually mark and measure 203 breeding adult Mangrove Warblers across their breeding ranges at 9 study areas in Baja California Sur and Sonora, Mexico. I summarized morphometric measurements using Principal Component Analysis (PCA) and performed Multivariate Analysis of Variance (MANOVA) to test if differences existed between subspecies, sex, and study areas. Results conclude S. p. castaneiceps is different from S. p. rhizophorae (P=\u3c0.001), such that S. p. castaneiceps was a larger subspecies. Males were larger than females (P=\u3c0.001) in both subspecies and variation existed among study areas in S. p. castaneiceps (P=0.001) and S. p. rhizophorae (P=\u3c0.001). After finding significance among study areas, we then used SAS 9.2 to run MANOVA with post-hoc contrasts for each morphometric measurement within a subspecies. We found the Pacific Coast populations of S. p. castaneiceps to be generally larger than the western coast Sea of Cortez populations. The northernmost population for S. p. rhizophorae was smaller overall compared to the other populations sampled in Sonora.;The S. p. castaneiceps banded population was re-sighted during wintering (2010) and breeding (2011) periods to examine localized, year-round movements. Waypoints of breeding (2010 and 2011) and wintering (2010) locations were mapped and analyzed using ArcMap 9.3.1 to determine localized movements within the population. Results suggest the Mangrove Warbler has limited, if any, year-round movements. No movement was found among mangrove stands, but territory switching was found to occur within a mangrove stand between the wintering and breeding season. There was high territory replacement among the entire population suggesting that there may be high occurrence of floaters. Re-sighting surveys and capture events were used to calculate density of males, females and pairs per mangrove site. There were no significant changes in population density between seasons (P=0.07), but males averaged a higher year-round density compared to females and pairs (P=0.02)