Resource use and defence by ruby-throated hummingbirds during stopover

Zenzal, Theodore J.; Moore, Frank R.

doi:10.1163/1568539x-00003533

Cited by 5 publications

(3 citation statements)

References 49 publications

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“…The contrasting effect of temperature during the month of departure in ruby‐crowned kinglets, when both fuel load and departure day behave as response variables may be a result of the positive association between temperature and bird abundance (Lepthien and Bock 1976). During warmer months, a higher abundance of individuals in the non‐breeding area could depress fuel loads (Moore and Yong 1991, Kelly et al 2002, Zenzal and Moore 2019) and, consequently, delay the initiation of migration.…”

Section: Discussionmentioning

confidence: 99%

Local weather and endogenous factors affect the initiation of migration in short‐ and medium‐distance songbird migrants

Zenzal

Johnson

Moore

et al. 2023

Journal of Avian Biology

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Migratory birds employ a variety of mechanisms to ensure appropriate timing of migration based on integration of endogenous and exogenous information. The cues to fatten and depart from the non‐breeding area are often linked to exogenous cues such as temperature or precipitation and the endogenous program. Shorter distance migrants should rely heavily on environmental information when initiating migration given relatively close proximity to the breeding area. However, the ability to fatten and subsequently depart may be linked to individual circumstances, including current fuel load and body size. For early and late departing migrants, we investigate effects of temperature, precipitation, lean body mass, fuel load and day of year on the initiation of migration (i.e. fuel load and departure timing) from the non‐breeding region by analyzing 21 years of banding data for four species of short‐ and medium‐distance migrants. Temperatures at the non‐breeding area were related to temperatures at potential stopover areas. Despite local cues being predictive of conditions further north, the amount variation explained by local weather conditions in our models differed by species and temporal period but was low overall (< 33% variation explained). For each species, we also compared lean body mass and fuel load between early and late departing migrants, which showed mixed results. Our combined results suggest that most individuals migrating short or medium distances in our study did not time the initiation of migration with local predictive cues alone, but rather other factors such as lean body mass, fuel load, day of year, which may be a proxy for the endogenous program, and those beyond the scope of our study also influenced the initiation of migration. Our study contributes to understanding which factors influence departure decisions of short‐ and medium‐distance migrants as they transition from the non‐breeding to the migratory phase of the annual cycle.

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Section: Discussionmentioning

confidence: 99%

Local weather and endogenous factors affect the initiation of migration in short‐ and medium‐distance songbird migrants

Zenzal

Johnson

Moore

et al. 2023

Journal of Avian Biology

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“…Regardless of departure direction, most individuals left our edge site within 24 h of capture and, with our underlying assumption of less food at edge sites confirmed, individuals seeking to replenish energy stores would be more food limited and likely face increased competitor and predation pressure if remaining on the coast (Moore and Yong 1991, Aborn 1994, Woodrey and Moore 1997, Kelly et al 2002, Cimprich et al 2005, Cimprich and Moore 2006, Moore et al 2017, Zenzal and Moore 2019. A third of the departing individuals engaged in retreating movements consistent with locating more suitable stopover habitat, based on our food data -a behavior associated with the feeding state.…”

Section: Departing the Edgementioning

confidence: 91%

“…Migrants departing edge sites often select departure directions inconsistent with progress toward their breeding or non‐breeding destination (Alerstam 1978, Åkesson et al 1996, Åkesson 1999, Smolinsky et al 2013, Woodworth et al 2014, Deppe et al 2015, Nilsson and Sjöberg 2016). Coastlines, for example, are often characterized as habitat‐poor landscapes with high concentrations of migrants, which leads to reduced habitat quality (Abdollahi et al 2005, Mehlman et al 2005, Schaub et al 2008, Buler and Moore 2011, Lain et al 2017) in terms of increased predation pressure (Aborn 1994, Cimprich et al 2005, Woodworth et al 2014) and competition for food (Moore and Yong 1991, Zenzal and Moore 2019). Ultimately, if individuals are unable to adequately prepare for a long distance flight in edge habitats, then they will have a lower survival probability when attempting to cross the potential barrier (Erni et al 2003, Ward et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Retreat, detour or advance? Understanding the movements of birds confronting the Gulf of Mexico

Zenzal

Ward

Diehl

et al. 2021

Oikos

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During migration, birds must locate stopover habitats that provide sufficient resources to rest and refuel while en route to the breeding or non-breeding area. Long-distance migrants invariably encounter inhospitable geographic features, the edges of which are often characterized by habitat limited in food and safety. In response, they often depart in directions inconsistent with reaching their destination, presumably searching for better habitat. We used automated radio telemetry to track 442 individuals of five species to investigate the behavior of migratory birds as they departed edge habitat along the northern Gulf of Mexico coast during autumn from 2008 to 2014. Most migrants (75%) retreated inland or detoured around rather than advanced across the Gulf, but this depended on bird species and fat-based energy stores. Most individuals in lean condition or of smaller bodied species tended to retreat or detour, rather than advance, when departing from the coast. Twenty-one percent of all birds that departed the coast in 2013-2014 were redetected over 45 km inland, providing a unique opportunity to compare stopover duration, departure times and travel speeds between migrants that retreat away from the coast and those that continue to advance toward their destination. Individuals that retreated the coast and were redetected inland spent ~1 day on the coast before retreating inland, where they spent 11 days before resuming migration. Further when those same individuals retreated from the coast, they departed around evening civil twilight, whereas those that advanced from inland habitats departed after evening civil twilight. Travel speeds were slower for individuals retreating inland compared to those advancing towards the coast from inland habitats. The differences between retreating and advancing individuals suggest how an individual's drive to feed or fly influences behavior. Our study illustrates how the sum of individual decisions can shape habitat use, landscape-scale movements and migration strategies.

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Stopover territoriality in songbirds crossing the Sahara: aggression and energetics during migration

Aispuro

Canoine

Illa

et al. 2023

Behav Ecol Sociobiol

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Stopover territoriality, i.e., the defense and broadcast of an ephemeral home range during avian migration, is rare or perhaps overlooked. However, settling on a territory may allow for easier access to resources and therefore promote faster refueling despite the added costs of territory defense. We examined the occurrence of stopover territoriality and its relationship to body condition and refueling rates. We color-ringed Western Subalpine Warblers (Curruca iberiae) mapped their home ranges and measured associated habitat characteristics during a spring stopover in the Sahara. We simulated territory intrusions via song playback to quantify territorial behavior. Males aggressively defended and broadcasted their stopover territories in response to intruders. Initial body condition in males was negatively related to home range vegetation density, suggesting that males in higher condition are selective for certain territory features. Low vegetation density does not support habitat selection for foraging, but perhaps does support social monitoring or predator vigilance as its functions. Fuel deposition rates in recaptured males were unrelated to home range habitat characteristics. Female Subalpine Warblers did not use repeated home ranges yet had similar refueling rates, body conditions, and stopover durations as territorial males. Therefore, while stopover territories were selected based on body condition, territory characteristics did not influence refueling rates. Subalpine Warblers expressed reduced migratory characteristics, making prolonged stopovers of up to 27 days with low refueling rates but maintaining body condition while defending territories. These results suggest that some individuals are staging for non-energetic reasons, such as pre-breeding preparations, or transitioning between a migratory and a breeding life history stage. Significance statement Territoriality in birds is commonly associated with breeding activities, less so with the wintering period and rarely with migratory periods. However, territoriality during migration may be energetically beneficial. During a trans-Saharan stopover, male warblers establish and defend temporary territories by singing and engaging in physical defense of home ranges, and those in better condition occupied territories with sparser vegetation. Females were not territorial but refueled at similar rates as males. Stopover territoriality did not increase access to food-rich patches, but perhaps aided in efficient social monitoring and preparations for the approaching breeding season. This is the first detailed documentation of birds defending ephemeral territories during migration, and its potential functions, costs and benefits may inform studies of full-annual cycles and life histories of many migratory species.

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Resource use and defence by ruby-throated hummingbirds during stopover

Cited by 5 publications

References 49 publications

Local weather and endogenous factors affect the initiation of migration in short‐ and medium‐distance songbird migrants

Local weather and endogenous factors affect the initiation of migration in short‐ and medium‐distance songbird migrants

Retreat, detour or advance? Understanding the movements of birds confronting the Gulf of Mexico

Stopover territoriality in songbirds crossing the Sahara: aggression and energetics during migration

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