Baseline Hematocrit Values in Birds: an Important Tool for Monitoring Exposure to Polycyclic Aromatic Hydrocarbons

Avian hematocrit can be used to monitor the effects of polycyclic aromatic hydrocarbons during the aftermath of oil spills and their cleanup.Exposure to PAHs can result in a rapid and dramatic drop in hematocrit.Some baseline hematocrit data has been reported for waterbirds before and during coastline spills, but the equivalent baseline hematocrit data does not exist for monitoring land-based spills affecting migratory and resident songbirds.In this study, blood samples were taken from 310 North American migratory birds on their wintering grounds in The Bahamas and Panama.Hematocrit was measured in 20 species of passerines and near passerines plus one shorebird species.The results show that hematocrit values rose prior to northbound migration in mid-March to mid-April when samples were compared to those taken in January.Among those species able to be reliably sexed by plumage, increases in hematocrit were found only in males.Hematocrit samples from 8 neo-tropical species and one avian family met new guidelines for determining reference intervals as published by The American Society of Veterinary Clinical Pathologists.This study establishes hematocrit baseline values for a portion of the annual cycle of these neo-tropical migrant species and explains how monitoring changes in hematocrit after polycyclic aromatic hydrocarbon exposure can be used to determine injury and possible recovery after an oil spill.