Repeatability and Validity of Phenotypic Trait Measurements in Birds

Subasinghe, Kalya; Symonds, Matthew R. E.; Vidal‐García, Marta; Bonnet, Timothée; Prober, Suzanne M.; Williams, Kristen J.; Gardner, Janet L.

doi:10.1007/s11692-020-09527-5

Cited by 6 publications

(2 citation statements)

References 67 publications

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“…We measured bill depth, width and length from each specimen, as well as length of the closed wing (hereafter 'wing length') (Stiles and Altshuler 2004), which we used as a proxy for individual body size. We used digital calipers to measure wing length, but because many thrasher species have curved bills, caliper measurements would not capture the full curved length of the bill (but see Subasinghe et al 2021). Therefore, we photographed each bill from a dorsal and profile view against a gridded background using a mounted Canon Rebel DSLR camera.…”

Section: Specimen Measurementsmentioning

confidence: 99%

Effects of climate on bill morphology within and across Toxostoma thrashers

Probst

Ralston

Bentley

2021

Journal of Avian Biology

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Bird bills possess an important thermoregulatory function as they are a site for environmental heat exchange. Previous studies have demonstrated that birds in warmer climates have larger bills than those living in colder climates, as larger bills can dissipate more heat. Because this dry heat transfer does not incur water loss, it may be additionally advantageous in water-restricted habitats. Here, we examine the influence of climate on bill morphology in Toxostoma thrashers, a group of 10 North American species that varied in bill morphology and occupied climate niche, with several species inhabiting arid climates. Past examinations of thrasher bill morphology have only considered foraging, leaving unanswered the role of climate in morphological divergence within this group. We photographed 476 Toxostoma museum specimens encompassing all 10 species and calculated bill measurements from the photos using a MATLABbased program. For each species, we calculated occupied climate niche using data from WorldClim describing temperature and precipitation. We found no reliable significant relationships between climate variables and bill morphology across species, suggesting that other factors such as foraging behavior may be more important in shaping bill morphology in this genus. Within species, we found three Toxostoma species have significant relationships between bill morphology and climate that follow Allen's rule. However, we also found the relationships between climate and bill morphology varied in strength and direction across species. Notably, we found a negative relationship between maximum temperature of the hottest month and bill surface area in LeConte's thrasher, which occupies the hottest and most arid climates of the thrashers. This adds to the evidence that Allen's rule may reverse in extremely hot climates when the bill may become a heat sink instead of a heat radiator. These results demonstrate the importance of considering the generality of ecogeographical rules across lineages that occupy extreme climates.

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Section: Specimen Measurementsmentioning

confidence: 99%

Effects of climate on bill morphology within and across Toxostoma thrashers

Probst

Ralston

Bentley

2021

Journal of Avian Biology

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“…One challenge with ascertaining changes in body size is that there are several alternative ways of measuring it. In birds, absolute wing length is highly correlated with body mass 34 and underlying bone length 35 and has therefore been considered an indicator of structural body size that is more stable than mass 33, 36 . Indeed, many studies on Bergmann’s rule find that absolute wing length decreases with lower latitudes 8 .…”

Section: Introductionmentioning

confidence: 99%

Pervasive morphological responses to climate change in bird body and appendage size

Ryding,

McQueen,

Klaassen

et al. 2023

Preprint

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Changes to body size and shape have been identified as potential adaptive responses to climate change, but the pervasiveness of these responses is questioned. To address this, we measured body and appendage size from 5013 museum bird skins of ecologically and evolutionary diverse species. We found that morphological change is a shared response to climate change across birds. Birds increased bill surface area, tarsus length, and relative wing length through time, consistent with expectations of increasing appendage size in warmer climates. Furthermore, birds decreased in absolute wing length, consistent with the expectation of decreasing body size in warmer climates. Interestingly, these trends were generally consistent across different diets, foraging habitats, and migratory and thermoregulatory behaviours. Shorter-term responses to hot weather were contrary to long-term effects for appendages. Overall, our findings support that morphological adaptation is a widespread response to climate change in birds that is independent of other ecological traits.

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