Constitutive immune function in European starlings,Sturnus vulgaris, is decreased immediately after an endurance flight in a wind tunnel

Abstract

SUMMARYLife-history theory predicts that animals face a trade-off in energy allocation between performing strenuous exercise, such as migratory flight, and mounting an immune response. We experimentally tested this prediction by studying immune function in European starlings, Sturnus vulgaris, flown in a wind tunnel. Specifically, we predicted that constitutive immune function decreases in response to training and, additionally, in response to immediate exercise. We compared constitutive immune function among three groups: (1) ʻuntrainedʼ birds that were kept in cages and were not flown; (2) ʻtrainedʼ birds that received flight training over a 15day period and performed a 1-4h continuous flight, after which they rested for 48h before being sampled; and (3) ʻpost-flightʼ birds that differed from the ʻtrainedʼ group only in being sampled immediately after the final flight. A bird in our trained group represents an individual during migration that has been resting between migratory flights for at least 2days. A bird in our post-flight group represents an individual that has just completed a migratory flight and has not yet had time to recover. Three of our four indicators (haptoglobin, agglutination and lysis) showed the predicted decrease in immune function in the post-flight group, and two indicators (haptoglobin, agglutination) showed the predicted decreasing trend from the untrained to trained to post-flight group. Haptoglobin levels were negatively correlated with flight duration. No effect of training or flight was detected on leukocyte profiles. Our results suggest that in European starlings, constitutive immune function is decreased more as a result of immediate exercise than of exercise training. Because of the recent emergence of avian-borne diseases, understanding the trade-offs and challenges faced by long-distance migrants has gained a new level of relevance and urgency.

Plasticity of immunity in response to eating

“…agglutination increased within 24 h of the onset of absorption), which is in accordance with previous work (e.g. hemolysis and hemoagglutination are reduced after a flight lasting ≤4 h in European starlings, Sturnus vulgaris: Nebel et al, 2012). These findings suggest a temporally dynamic innate immune system (sensu Zylberberg, 2015) that responds to food consumption.…”

First evidence of a 200-day non-stop flight in a bird

“…To date, long-lasting flights have been investigated under the aspect of fasting during flight 22 . Recent studies showed that immune responses seem to be affected by long-lasting flights 23 . Alpine swifts feed on the wing and might be able to compensate such negative effects on immune defence.…”

Flight performance of western sandpipers Calidris mauri remains uncompromised when mounting an acute phase immune response

“…The limited empirical evidence to date suggests that migrating birds do not appear to reduce their flight performance as a consequence of mounting an immune response. Immune function, in contrast, has been shown to diminish after strenuous flights in western sandpipers, European starlings and red knots (Buehler et al, 2010;Nebel et al, 2012).…”

“…Likewise, a recent study on European starlings, Sturnus vulgaris, showed a negative relationship between strenuous exercise and immune function. Non-induced aspects of immune function (plasma levels of haptoglobin, agglutination and lysis) decreased significantly after flight in a wind tunnel (Nebel et al, 2012). The effects of strenuous exercise on immune function likely vary among different aspects of the immune system.…”