NEWMAN, S.H., CARTER, H.R., WHITWORTH, D.L. & ZINKL, J.G. 2005. Health assessments and stress response of Xantus’s Murrelets to capture, handling, and radio-marking. Marine Ornithology 33: 147-154.

Physiological health of Xantus’s Murrelets Synthliboramphus hypoleucus, a seabird of conservation concern in the United States and Mexico, has received little attention. In 1994-97, we collected blood samples from murrelets attending nocturnal at-sea congregations adjacent to Santa Barbara Island, California, to establish baseline health indices. Hematologic and serum biochemical indices were similar to other small alcids, except for lower creatine kinase activity, higher lactate dehydrogenase activity, and higher uric acid concentration. To determine whether minimally invasive procedures for capture, handling and radio-marking pose a health risk to murrelets, we also assessed the acute stress response. Serum corticosterone, white blood cell counts (heterophils, lymphocytes, monocytes, eosinophils, and basophils), and heterophil:lymphocyte ratio (H:L ratio) were used as biochemical and cellular indicators of stress. Corticosterone levels measured 30 min after capture (49 ± 22 ng/dl) were significantly higher than those measured within 3 min of capture (22 ± 21 ng/dl), indicating a stress response. However, at 30 min post-capture, neither handling (prior to blood collection) nor sedation with Isoflurane gas and radio-marking (subcutaneous anchor method) resulted in significantly higher mean corticosterone levels, indicating that the stress response was not greater in magnitude due to these additional procedures. White blood cell counts did not differ among any 30-min study groups, but heterophil counts were higher, lymphocyte counts lower, and the H:L ratio higher for birds that were sedated and radio-marked. The magnitude of the stress response was not excessive relative to other handling protocols and probably did not cause changes to bird behavior post-release.

Key words: Xantus’s Murrelet, blood, health, stress, hematology, biochemistry, corticosterone, heterophil, telemetry, radio-marking, Synthliboramphus hypoleucus