Meeting Abstract
Migratory birds increase hematocrit (Hct) prior to initiating long distance flight, presumably to increase blood oxygen carrying capacity to sustain high intensity exercise. Despite widely held assumptions that Hct is a key determinant of aerobic capacity and exercise performance, their relationship has not often been tested rigorously and results to date are mixed. Furthermore, it is known that although passerines spend the majority of time flying at low altitude (<800m) during migratory flight, they do sometimes fly at higher altitudes depending on winds and weather (up to 4000m). However, most studies investigating physiology of migration have been conducted at low altitude and have largely ignored the transient but potentially important altitude component. To examine the effects of experimental manipulation of Hct on flight performance, we treated yellow-rumped warblers (Setophaga coronata) with avian erythropoietin (EPO), erythropoietin antibody (anti-EPO) and saline and assessed flight performance with wind tunnel flights. We also conducted short altitude challenges using a hypobaric wind tunnel to look at effects of EPO and anti-EPO on performance and physiological response to elevated altitude. We collected blood samples upon completion of each flight for Hct, blood glucose and oxidative stress measurements. Preliminary data suggest that while EPO-treated birds performed marginally better than anti-EPO and saline treated birds during endurance flight at low altitude, anti-EPO treated birds were better able to sustain flights at higher altitudes than saline and EPO treated birds. We also observed increased glucose and decreased Hct in response to flight at altitude, regardless of treatment. Assessment of oxidative stress will be also be reported on as a potential physiological costs of endurance flight.
