Using automated radio telemetry to quantify activity patterns of songbirds during stopover

Schofield, Lynn N.; Deppe, Jill L.; Zenzal, Theodore J.; Ward, Michael P.; Diehl, Robert H.; Bolus, Rachel T.; Moore, Frank R.

doi:10.1642/auk-17-229.1

Cited by 20 publications

(24 citation statements)

References 52 publications

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“…Stopovers serve to accumulate fuel, but are also typically thought to allow migrants to 'rest' and recover from migratory endurance flight (e.g. [38][39][40][41][42][43][44][45]), even though within-individual data to substantiate this hypothesis have, until now, been lacking.…”

Section: Discussionmentioning

confidence: 99%

Migrating birds rapidly increase constitutive immune function during stopover

2020

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Migratory flight is physiologically highly demanding and has been shown to negatively affect multiple parameters of constitutive immune function (CIF), an animal's first line of physiological defence against infections. In between migratory flights, most birds make stopovers, periods during which they accumulate fuel for the next flight(s). Stopovers are also commonly thought of as periods of rest and recovery, but what this encompasses is largely undefined. Here, we show that during stopover, northern wheatears Oenanthe oenanthe, a long-distance migratory bird, can rapidly increase constitutive innate immune function. We caught and temporarily caged birds under ad libitum food conditions at a stopover site in autumn. Within 2 days, most birds significantly increased complement activity and their ability to kill microbes. Changes in immune function were not related to the birds' food intake or extent of fuel accumulation. Our study suggests that stopovers may not only be important to refuel but also to restore immune function. Additionally, the increase in CIF could help migrating birds to deal with novel pathogens they may encounter at stopover sites.

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Section: Discussionmentioning

confidence: 99%

Migrating birds rapidly increase constitutive immune function during stopover

2020

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“…Our experimental design does not allow to conclude that the reduced locomotor activity is functional to increase energy saving, although this interpretation appears plausible. For example, reduction of movement as an energy saving strategy has been suggested for migratory birds stopping over in proximity of an ecological barrier 59,60 .…”

Section: Discussionmentioning

confidence: 99%

The amount of available food affects diurnal locomotor activity in migratory songbirds during stopover

Ferretti

Maggini

Lupi

et al. 2019

Sci Rep

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Migratory passerine birds fly long distances twice a year alternating nocturnal flights with stopovers to rest and replenish energy stores. The duration of each stopover depends on several factors including internal clocks, meteorological conditions, and environmental factors such as availability of food. Foraging entails energetic costs, and if birds need to refuel efficiently, they should modulate their activity in relation to food availability. We investigated how food availability influences locomotor activity in migrating birds of six passerine species at a spring stopover site in the central Mediterranean Sea. We selected birds with low fat scores which we expected to be strongly motivated to refuel. We simulated stopover sites of different quality by providing temporarily caged birds with different amounts of food to simulate scarce to abundant food. We analysed the diurnal locomotory activity as a proxy for food searching effort. Low food availability resulted in an increased diurnal locomotor activity in almost all species, while all birds showed low intensity of nocturnal migratory restlessness. In conclusion, our study shows that food availability in an important determinant of behaviour of migratory birds at stopover sites.

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“…By using the amount of diurnal locomotion as a proxy for food searching behavior (Morton 1967;Astheimer et al 1992;Fokidis et al 2011), we found that a few species show an intense diurnal activity regardless of food availability, whereas most of the species increased locomotor activity with decreasing amount of food (Ferretti et al 2019a). Although it appears plausible that the reduction of diurnal locomotion in response to food availability has an energy-saving function (Bäckman et al 2016;Schofield et al 2018) -as suggested by the comparison of metabolic data between migrating birds displaying different behaviors (Ferretti et al 2019b), our current knowledge does not allow to rule out that reduction in locomotion is also functional to reduce potential predation risk. Indeed, birds that find limited food sources are expected to increase their activity in the attempt to improve refueling (Cohen et al 2012;Ferretti et al 2019a), although this strategy may increase their exposure to potential predators (Lima 1986;Lind & Cresswell 2006).…”

Section: Energy Management On Small Islandsmentioning

confidence: 94%

How to recover after sea crossing: the importance of small islands for passerines during spring migration

Ferretti

Maggini

Fusani

2021

Ethology Ecology & Evolution

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Every year, billions of migratory birds cover thousands of kilometers between their wintering grounds and their breeding areas. Along their migratory route, birds are often forced to break up their journey into several legs, mainly in correspondence with ecological barriers (e.g. seas and deserts), and stopover in areas where they can sleep and rebuild their energy stores. Stopover is a key migratory stage for many songbirds because strategies adopted at this stage may have direct bearing on the success of migration and, consequently, on the fitness of the individual. Although the restoration of energy reserves is likely the main goal for stopover in many cases, our recent studies suggest that there might be other reasons for stopping over, particularly after long non-stop flights. This seems to be the case of millions of songbirds that land on small coastal islands after crossing large waterbodies, although most of these sites do not provide sufficient refueling opportunities. Here, we aim to provide a new perspective on the role of such small islands by reviewing our recent findings on energy management in migratory songbirds. We are convinced that understanding the role of these islands for migratory birds, as well as how birds manage their energy at these sites, represents an important step toward an optimization of conservation strategies, since setting priorities for protection based on food availability alone may miss critical functions of stopover sites.

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Using automated radio telemetry to quantify activity patterns of songbirds during stopover

Cited by 20 publications

References 52 publications

Migrating birds rapidly increase constitutive immune function during stopover

Migrating birds rapidly increase constitutive immune function during stopover

The amount of available food affects diurnal locomotor activity in migratory songbirds during stopover

How to recover after sea crossing: the importance of small islands for passerines during spring migration

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