Optimal stopover model: A state‐dependent habitat selection model for staging passerines

Abstract

1. During their seasonal migration, birds stage in areas comprising stopover sites of varying quality. Given that migrating birds have a limited information about their environment, they may land at a low-quality stopover site in which their fuel deposition rate (FDR) is low. Birds landing at such sites should decide either to extend their stopover duration or to quickly depart in search for a better site. These decisions, however, strongly depend on their body condition upon landing. 2. To understand the decision-making process of passerines within a stopover area, comprising stopover sites of varying quality, prior to the crossing of a large ecological barrier, we constructed a state-dependent habitat selection model. The model assumes that even if migrating birds have an expectation of encountered area quality, they cannot control for their initial landing site. Once landing, movement between low-and high-quality stopover sites will occur only if the body condition of these birds is high to the extent that they can entail the energetic cost of movement. Birds in the model aim to maximize their fuel load at the end of the stopover period, to suffice for successfully crossing a large ecological barrier.3. The model is based on empirical data on autumn migrating Blackcaps Sylvia atricapilla, collected at two important stopover sites in the Negev desert of Israel.Migrating passerines staging at these two sites differ in their FDR and body condition. The model shows that the optimal behaviour when arriving at a low-quality stopover site is to abandon it quickly. However, as lean individuals cannot entail the costs of searching for an alternative site, they have no other choice but to stay there even if their chances to successfully cross the Sahara Desert ahead are low. 4. Our model can be applied to other ecological systems. Proper use of this model may allow good assessment of stopover site quality, as indicated by the bird's FDR, regardless of specific site characteristics. Hence, it can help applying targeted management decisions regarding the maintenance of stopover sites or establishment of new ones.

Comparative analysis of the plasma metabolome of migrating passerines during stopover: Novel insights into flight metabolism

“…In this way, lactic acid, glucose, and glycerol are examples of metabolites that were previously demonstrated to vary between birds before and after resting (Viswanathan et al 1987, Jenni-Eiermann andJenni 1992). Our previous research efforts (Domer et al 2018(Domer et al , 2021 have…”

“…In this way, lactic acid, glucose, and glycerol are examples of metabolites that were previously demonstrated to vary between birds before and after resting (Viswanathan et al 1987, Jenni-Eiermann and Jenni 1992). Our previous research efforts (Domer et al 2018, 2021) have shown that during autumn migration, both recapture and fuel accumulation rates are higher in ER than in BGS. These findings, in combination with the results presented here, strongly suggest that most birds at BGS leave soon after arrival (i.e., do not spend another night at this site) while most birds in ER are at a resting/refueling state.…”

“…Migratory birds alternate between two extreme physiological states, fasting during the long-distance endurance flights and resting or extensively feeding during stopovers (McWilliams and Karasov 2005). Hence, selecting a proper stopover site is crucial for long-distance migrants as low fuel deposition rates can extend their total migration period and affect their fitness (Gómez et al 2017, Domer et al 2021). We present an in-depth comparative analysis of the untargeted metabolomic profiling of wild migratory passerines sampled in the eastern Mediterranean region during autumn, along one of the most important flyways in the old world.…”

Drivers of migrant passerine composition at stopover islands in the western Mediterranean

“…On the contrary, small Mediterranean islands offer a very limited variety of dry scrublands, where fuel deposition rates have been found to be lower than in large Balearic Islands 21 . Migrating passerines arriving at unfamiliar stopover areas must base their choices on instant decisions 58 and island area may be a quick and easy indicator to use. Low-quality stopover sites can act as an ecological trap, especially for migrating birds with insufficient fuel load to leave in search for an alternative place of a higher quality 58 .…”

“…Migrating passerines arriving at unfamiliar stopover areas must base their choices on instant decisions 58 and island area may be a quick and easy indicator to use. Low-quality stopover sites can act as an ecological trap, especially for migrating birds with insufficient fuel load to leave in search for an alternative place of a higher quality 58 . Moving to an alternative stopover site may be even more costly and unpredictable when crossing the sea, thus the use of cues for improving the chance of selecting a high-quality island or avoiding low quality ones would be highly rewarding.…”