Abstract:Molt is energetically demanding and various molt strategies (i.e., molt series, duration, intensity, timing, and location) have evolved to reduce the negative fitness consequences of this process. As such, molt varies considerably among species. Identifying where and when specific feathers are molted is also crucial to inform species‐specific studies using stable isotope markers to assign individuals to geographical regions where they molt. Using museum specimens, we examined the molt of three species of migra… Show more
“…Despite the potential increase in fitness that would be afforded by migratory double breeding, the energetic and physiological demands of this process may be too great for it to be biologically possible. Moreover, cliff swallows undergo a protracted period of feather molt lasting around 160 days, 25 which may constrain other aspects of the annual cycle 9,14 and preclude a second breeding season in a single annual cycle. Upon arrival in Argentina, the six cliff swallows we studied did not show any sign of molt and none of the 18 trapped birds was in active molt during the breeding season (J.I.A.…”
Section: Phenological Changes In Molt and Breedingmentioning
“…Despite the potential increase in fitness that would be afforded by migratory double breeding, the energetic and physiological demands of this process may be too great for it to be biologically possible. Moreover, cliff swallows undergo a protracted period of feather molt lasting around 160 days, 25 which may constrain other aspects of the annual cycle 9,14 and preclude a second breeding season in a single annual cycle. Upon arrival in Argentina, the six cliff swallows we studied did not show any sign of molt and none of the 18 trapped birds was in active molt during the breeding season (J.I.A.…”
Section: Phenological Changes In Molt and Breedingmentioning
“…Birds were fitted with a uniquely numbered U.S. Geological Survey metal leg band. We measured unflattened wing chord to the nearest millimeter and plucked one or two inner tail feathers (R3 or R4) from each bird, which we assumed were moulted on the wintering grounds for stable isotope analysis [ 51 , 52 ]. Fig.…”
Section: Methodsmentioning
confidence: 99%
“…With probabilistic spatial models, combined use of multiple isotopes can be particularly insightful when spatial variation in a single isotope is not sufficient to assess origins across vast isotopic landscapes [ 8 , 34 , 50 ]. The use of stable isotopes to infer non-breeding origins is useful for several swallow species and other aerial insectivores because they molt during the non-breeding period [ 51 , 52 ].…”
Aerial insectivorous birds have suffered steep population declines in North America over the last 60 years. A lack of information on migratory connectivity between breeding and non-breeding grounds for these species limits our ability to interpret factors affecting their population-specific trends. We determined likely Latin American non-breeding regions of Bank (Riparia riparia), Barn (Hirundo rustica) and Cliff (Petrochelidon pyrrhonota) swallow from populations across their breeding ranges. We used predicted feather hydrogen (δ2Hf) and carbon (δ13Cf) isoscapes for winter-grown feathers to indicate areas of highest probability of moult origin and incorporated these results into a cluster analysis to determine likely broad non-breeding regions. We also assessed variation in wing length among populations to determine the potential for this metric to differentiate population moult origins. We then investigated patterns of multi-isotopic (δ2Hf, δ13Cf, δ15Nf) and wing-length niche occupancy by quantifying niche size and overlap among populations under the assumption that broad niches were consistent with low within-species migratory connectivity and narrow and non-overlapping niches with higher connectivity. Multivariate assignment identified different non-breeding regions and potential clusters of moult origin generally corresponding to Central America and northern South America, eastern and south-central South America, and the western and southern part of that continent, with variation within and among populations and species. Separate niche space indicated different wintering habitat or areas used by species or populations whereas niche overlap indicated only potential spatial similarity. Wing length varied significantly among populations by species, being longer in the west and north for Bank and Cliff Swallow and longer in eastern Canadian Barn Swallow populations. Barn Swallow occupied consistently larger isotopic and wing length niche space than the other species. Comparisons among populations across species showed variable isotopic and wing-length niche overlap generally being greater within breeding regions and lower between western and eastern breeding populations supporting a general North American continental divide for all species with generally low migratory connectivity for all species. We present a novel approach to assessing connectivity using inexpensive and broad isotopic approaches that provides the basis for hypothesis testing using more spatially explicit expensive techniques.
“… Shugart & Rohwer (1996) show the primaries of night herons constitute a single replacement series, and that primary replacement in adults is stepwise, with up to four waves proceeding simultaneously through the 10 primaries. Silveira & Marini (2012) show the primaries of a puffbird are divided into two molt series, and two swallows and a kingbird replace their outermost rectrix, R6, as a unique series independent of the timing of molt completion for the other five rectrices ( Yuri & Rohwer, 1997 ; Imlay et al, 2017 ; Rohwer, 2008 ).…”
Molt summary tables reveal the sequence and mode of flight-feather replacement and how these feathers are divided into independent replacement series. Tables for summarizing molt are relatively new, and the rules for generating them were first formally illustrated using data from a temperate passerine. However, this first illustration failed to address (i) species with primaries divided into more than one replacement series, (ii) species with stepwise primary replacement, which almost always involves incomplete annual replacement of the primaries, and (iii) species with incomplete annual replacement within molt series characterized by single-wave replacement. Here, we review complications that arise in developing molt summary tables for such cases and we offer solutions that remove ambiguity about the direction that molt proceeds within a replacement series and about the recognition of nodal and terminal feathers that mark the beginning and end of molt series. We use these modified molt summary tables to describe the sequence of primary replacement in four groups of Gruiform birds, a group for which primary replacement has been reported to proceed from the outermost primary toward the body, unlike most other birds. Eighty molting Grey-winged Trumpeters, Psophia crepitans, and 124 molting Limpkins, Aramus guarauna, show the sequence of primary replacement is proximal in both groups; furthermore, the primaries of trumpeters are divided into two replacement series, one beginning at the outermost primary P10, and the other beginning at P3. To further evaluate the extent of this highly unusual direction of replacement in Gruiforms, we cast the data (Stresemann & Stresemann, 1966) on primary replacement in upland rails (Rallidae) and flufftails (Sarothruridae) into molt summary tables; both also replace their primaries proximally, from outermost to innermost, suggesting that this mode of primary replacement may be characteristic of Gruiformes.
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