Structure, regulation, and evolution of Passerine molt

[eng] Molt is the process of plumage renewal by which birds maintain and adjust its functionality throughout their lifecycle. Multiple elements have been tackled in bird molt research (timing, duration, sequence, intensity, extent, feather growth rate, and plumage quality), but major gaps still exist on molt regulation, and especially on molt evolution. This thesis focuses on one molt element extensively recorded since mid-20th century but seldom studied as an individual trait: the set of feathers replaced after a given molt episode by one individual (here referred to as final molt phenotype). This is surprising because feathers differ in their function (e.g. signaling, thermoregulation, contribution to different flight functions, durability), costs of production, and morphology (e.g. exposure, mass, shape), all of which can be targeted by natural selection. Therefore, the final molt phenotype should be under strong selective pressures, suggesting that its regulation has been shaped during evolution to optimize plumage performance throughout the bird’s lifecycle. This thesis explores the potential of analyzing final molt phenotypes as is (instead of being analyzed partially or indirectly) to uncover underlying mechanisms of molt regulation and to provide insights on the evolution of molt in passerine birds. Following are the main findings presented in this thesis. Final molt phenotypes differed between the post-juvenile and the pre-breeding molts along the passerine phylogeny. A nested organization of final molt phenotypes suggested a rank of feather molt importance as underlying rule of molt. However, deviations from perfect nestedness were largely associated with the pre-breeding molt. Shared ancestry explained a large portion of final molt phenotype variation, likely due to constraints associated to plumage morphology, which is highly conserved in passerines. Phylogenetic analyses confirmed the phylogenetic independence of the pre-breeding molt and the strong phylogenetic signal of the post-juvenile molt. Further, they showed the overlooked relevance of environmental factors on the evolution of passerine molt, although their effect varied among taxonomic groups and molt episodes, thus highlighting the flexibility and adaptiveness of molt. Findings exposed in this thesis confirm the relevance of the final molt phenotype as a promising element to advance in our understanding of bird molt.[cat] La muda és el procés de renovació del plomatge mitjançant el qual els ocells mantenen i ajusten la seva funcionalitat durant tot el seu cicle vital. S’han abordat diversos elements en la investigació de la muda dels ocells (calendari, durada, extensió, intensitat, seqüència, qualitat del plomatge i velocitat de creixement de la ploma), però encara hi ha importants llacunes sobre la regulació de la muda i, sobretot, sobre la seva evolució. Aquesta tesi se centra en un element de la muda àmpliament registrat des de mitjan segle XX, però que encara no ha estat estudiat com a tret individual: el conjunt de plomes substituïdes després d’un determinat episodi de muda per un individu (aquí anomenat fenotip final de muda). Això és sorprenent perquè les plomes difereixen en la seva funció (e.g. senyalització, termoregulació, contribució al vol, durabilitat), costos de producció i morfologia (e.g. exposició, massa, forma), que poden ser objecte de selecció natural. Per tant, el fenotip de muda final hauria d’estar sota fortes pressions selectives, cosa que suggereix que la seva regulació s’ha configurat durant l’evolució per optimitzar el rendiment del plomatge al llarg del cicle de vida de l’ocell. Aquesta tesi explora el potencial d'analitzar el fenotip de muda final tal com és (en lloc d'analitzar-lo parcialment o indirectament) per descobrir els mecanismes subjacents de regulació de la muda i proporcionar informació sobre l'evolució de la muda en els passeriformes. A continuació es mostren les principals conclusions presentades en aquesta tesi. El fenotip de muda final diferia entre la muda post-juvenil i la pre-nupcial al llarg de la filogènia dels passeriformes. Una organització aniuada del fenotip de muda final va suggerir l’existència d’un rang d'importància en la muda de les plomes com a regla subjacent. Tanmateix, les desviacions de l’aniuament perfecte es van associar en gran mesura amb la muda pre-nupcial. L'ascendència compartida explicava una gran part de la variació del fenotip de muda final, probablement a causa de restriccions associades a la morfologia del plomatge, la qual està molt conservada en els passeriformes. Les anàlisis filogenètiques van confirmar la independència filogenètica de la muda pre- nupcial i l’elevat senyal filogenètic de la muda post-juvenil. A més, van mostrar la rellevància que han tingut els factors ambientals en l’evolució de la muda dels passeriformes, tot i que el seu efecte varia entre els grups taxonòmics i també entre els episodis de muda, destacant així la flexibilitat i la naturalesa adaptativa de la muda. Les troballes exposades en aquesta tesi confirmen la rellevància del fenotip de muda final com un element prometedor per avançar en la nostra comprensió de la muda dels ocells

AGE DETERMINATION OF AMETHYST‐THROATED HUMMINGBIRD (LAMPORNIS AMETHYSTINUS) AND WHITE‐EARED HUMMINGBIRD (HYLOCHARIS LEUCOTIS)

Abstract ∙ Age is one the most important parameters in avian biology, since life‐history strategies and population dynamics can be strongly influenced by age. Two characters are generally used to age hummingbirds (family Trochilidae): presence of maxillar striations and presence of beige to cinnamon fringes of dorsal feathers in the juvenile plumage. However, their applicability varies among species. For this reason, development and use of species specific criteria are highly recommended. Here, we describe age‐ and sex‐dependent variation of the central rectrix shape in Amethyst‐throated Hummingbird (Lampornis amethystinus) and White‐eared Hummingbird (Hylocharis leucotis). Juvenile central rectrices are more pointed than definitive ones. This criterion meets three crucial properties of aging techniques: high discriminant ability (78% for Amethyst‐throated Hummingbird and 99% for White‐eared Hummingbird), wide temporal applicability, and ease of use with minimum experience.Resumen ∙ Determinación de la edad del Colibrí Garganta Amatista (Lampornis amethystinus) y del Zafiro Oreja Blanca (Hylocharis leucotis) La edad es uno de los parámetros más importantes en el estudio de la biología de las aves, ya que tanto las estrategias vitales como la dinámica de poblaciones pueden estar fuertemente influidas por la edad. La edad de los colibríes (familia Trochilidae) se determina generalmente mediante dos caracteres: presencia de estrías maxilares y presencia de márgenes beige o canela en las plumas dorsales del plumaje juvenil. Sin embargo, su aplicabilidad varía entre especies. Por esta razón el desarrollo y empleo de criterios específicos adquiere relevancia. En este artículo describimos la variación en función de la edad de la forma de la rectriz central en el Colibrí Garganta Amatista (Lampornis amethystinus) y en el Zafiro Oreja Blanca (Hylocharis leucotis): las rectrices centrales juveniles son más puntiagudas que las rectrices definitivas. Este criterio reúne las tres propiedades cruciales que deben poseer las técnicas de determinación de la edad: capacidad discriminante elevada (78% en el Colibrí Garganta Amatista y 99% en el Zafiro Oreja Blanca), amplia aplicabilidad temporal y facilidad de uso con una experiencia mínima

Fichas de las especies

Sittasomus griseicapillus, Xiphorhynchus flavigaster, Myiopagis viridicata, Mitrephanes phaeocercus, Empidonax difficilis / occidentalis, Myiarchus tuberculifer, Myiarchus cinerascens, Myiarchus nuttingi, Myiarchus tyrannulus, Pitangus sulphuratus, Myiozetetes similis, Myiodynastes luteiventris, Pachyramphus aglaiae, Vireo brevipennis, Vireo bellii, Vireo nelsoni, Vireo hypochryseus, Vireo gilvus, Vireo flavoviridis, Thryothorus sinaloa, Thryothorus felix, Troglodytes brunneicollis, Troglodytes aedon, Henicorhina leucophrys, Polioptila caerulea, Myadestes occidentalis, Catharus aurantiirostris, Catharus occidentalis, Catharus frantzii, Catharus ustulatus, Turdus assimilis, Turdus rufopalliatus, Melanotis caerulescens, Vermivora celata, Vermivora ruficapilla, Vermivora crissalis, Parula superciliosa, Parula pitiayumi, Dendroica petechia, Dendroica coronata, Dendroica nigrescens, Dendroica townsendi, Dendroica graciae, Mniotilta varia, Seiurus aurocapilla, Seiurus noveboracensis, Seiurus motacilla, Oporornis tolmiei, Geothlypis trichas, Geothlypis poliocephala, Wilsonia pusilla, Cardellina rubrifrons, Myioborus miniatus, Basileuterus belli, Icteria virens, Granatellus venustus Piranga erythrocephala, Volatinia jacarina, Diglossa baritula, Atlapetes pileatus, Arremon virenticeps Arremonops rufivirgatus, Melozone kieneri, Pipilo ocai, Aimophila ruficauda, Melospiza lincolnii Saltator coerulescens, Pheucticus melanocephalus, Cyanocompsa parellina, Passerina leclancherii, Passerina versicolor, Passerina ciris, Icterus cucullatus, Icterus pustulatus, Icterus graduacauda Carduelis notat

PREFORMATIVE WING MOLT IN 23 NEOTROPICAL RESIDENT PASSERINE SPECIES

ABSTRACT ∙ Quantitative descriptions of wing‐feather replacement during the preformative and prealternate molts of resident Neotropical passerines are deficient: no more than 100 species possess adequate information. Here, we present quantitative molt data for 23 Neotropical passerines in three blocks: wing and tail molt extent, frequency of wing‐molt pattern, and frequency of wing‐feather replacement. We used Bayesian bootstrapping to estimate mean and 95% credible intervals of wing‐ and tail‐molt extent. We found four molt patterns in the preformative molt, of which most species present more than one. Twenty‐one species undergo partial molt, being the general pattern most frequent. Only Northern Beardless‐Tyrannulet (Camptostoma imberbe) and Black‐chested Sparrow (Peucaea humeralis) undergo a complete preformative molt, the latter also undergoing an extensive prealternate molt. Basic life‐history information may inspire hypotheses to explain molt phenomena. In this sense, our results suggest that lack of time constraints has a small influence on completeness of preformative molt, at least in Neotropical passerines.RESUMEN ∙ Muda preformativa de 23 especies residentes de paseriformes Neotropicales La deficiencia de descripciones cuantitativas sobre el reemplazo de plumas del ala en las mudas preformativa y prealterna de paseriformes neotropicales es dramática: no más de 100 especies poseen información adecuada. A continuación, presentamos datos cuantitativos de muda para 23 paseriformes neotropicales en tres bloques: extensión de muda en ala y cola, frecuencia de patrón de muda alar, y frecuencia de reemplazo de plumas del ala. Utilizamos “bootstrapping” bayesiano para estimar la media e intervalos de credibilidad del 95% de la extensión de muda en ala y cola. Encontramos cuatro patrones de muda en la muda preformativa, de los cuales la mayoría de las especies presentan más de uno. Veintiuna especies mostraron patrones parciales, siendo el patrón general el más frecuente. Sólo Camptostoma imberbe y Peucaea humeralis realizan una muda completa (este último también presenta una extensa muda prealterna). La información básica sobre historia natural puede inspirar hipótesis que expliquen los fenómenos de muda. En este sentido, nuestros resultados sugieren que la ausencia de limitaciones temporales tiene una influencia limitada sobre la compleción de la muda preformativa, al menos en paseriformes neotropicales. 

Resultados generales

Aspecto externo Morfometría esquelética y masa Morfometría alar y caudal Tamaño Estructuras sexuales externas Determinación del sexo Neumatización craneal Muda Datación mediante variables semicuantitativas Ciclos vitale

Activity and migration of Cory's shearwater

I describe some of the features that characterize the activity and migration of Cory's shearwater during approximately one year. I also explore the influence of Moon, photoperiod, geographic position and life-history stage on the resulting patterns and the periodicity of the latter. I have principally used time series and regression analysis. Its use here is one of the first applications to the analysis of logger data in seabirds. An intriguing finding of this work is the lunar periodicity that pervades the annual cycle of this species.En aquest treball descric alguns dels trets que caracteritzen l'activitat i la migració de la baldriga cendrosa durant aproximadament un any. També exploro la influència de la lluna, el fotoperíode, la posició geogràfica i l'etapa del cicle vital en els patrons resultants i la seva periodicitat. He utilitzat principalment sèries de temps i anàlisi de regressió. La seva utilització aquí és una de les primeres aplicacions per a l'anàlisi de dades recollides mitjançant geolocalitzadors en aus marines. Una troballa interessant d'aquest treball és la periodicitat lunar que domina el cicle anual d'aquesta espècie

Relative abundance and distribution of fisheries influence risk of seabird bycatch

Fisheries provide an abundant and predictable food source for many pelagic seabirds through discards, but also pose a major threat to them through bycatch, threatening their populations worldwide. The reform of the European Common Fisheries Policy (CFP), which intends to ban discards through the landing obligation of all catches, may force seabirds to seek alternative food sources, such as baited hooks from longlines, increasing bycatch rates. To test this hypothesis we performed a combined analysis of seabird-fishery interactions using as a model Scopoli's shearwaters Calonectris diomedea in the Mediterranean. Tracking data showed that the probability of shearwaters attending longliners increased exponentially with a decreasing density of trawlers. On-board observations and mortality events corroborated this result: the probability of birds attending longliners increased 4% per each trawler leaving the longliner proximity and bird mortality increased tenfold when trawlers were not operating. Therefore, the implementation of the landing obligation in EU waters will likely cause a substantial increase in bycatch rates in longliners, at least in the short-term, due to birds switching from trawlers to longliners. Thus the implementation of the landing obligation must be carefully monitored and counterbalanced with an urgent implementation of bycatch mitigation measures in the longline fleet

Activity and migration of Cory's shearwater

I describe some of the features that characterize the activity and migration of Cory’s shearwater during approximately one year. I also explore the influence of Moon, photoperiod, geographic position and life-history stage on the resulting patterns and the periodicity of the latter. I have principally used time series and regression analysis. Its use here is one of the first applications to the analysis of logger data in seabirds. An intriguing finding of this work is the lunar periodicity that pervades the annual cycle of this species.En aquest treball descric alguns dels trets que caracteritzen l'activitat i la migració de la baldriga cendrosa durant aproximadament un any. També exploro la influència de la lluna, el fotoperíode, la posició geogràfica i l'etapa del cicle vital en els patrons resultants i la seva periodicitat. He utilitzat principalment sèries de temps i anàlisi de regressió. La seva utilització aquí és una de les primeres aplicacions per a l'anàlisi de dades recollides mitjançant geolocalitzadors en aus marines. Una troballa interessant d'aquest treball és la periodicitat lunar que domina el cicle anual d'aquesta espècie

Moult nestedness and its imperfections: insights to unravel the nature of passerine wing-feather moult rules

Passerine moult shows two well-known although intriguing characteristics: 1) a varying subset of wing feathers are retained during certain moult episodes, and 2) the identity of the replaced feathers is not random. However, the rules that underlie these moult features are largely unknown. Non-randomness could arise under time and energy constraints if feathers differed in their importance, such that they could be ordered following a hypothetical moult rank. This rule predicts a nested relationship among wing-feather moult phenotypes, where phenotypes of smaller extent would consist of subsets of the wing feathers replaced in phenotypes of larger extent. Here, we analysed a dataset of 3909 preformative and prealternate moult phenotypes from 434 Holarctic and Neotropical passerine species. We found that passerine wing-feather moult was nested (nodf = 84.31). However, systematic imperfections in the nestedness pattern led us to test whether the existence of different feather moult ranks may increase nestedness in homogeneous subsets of moult phenotypes. We tested this hypothesis between moult episodes and found that nestedness increased for the preformative moult (nodf = 90.99) and decreased for the prealternate moult (nodf = 67.28). We further analysed the adaptive meaning of different moult ranks associated with feather mass, feather exposure and feather contribution to flight. Overall, these three feather traits explained 53.74% of the variation in the priority of wing-feather replacement, with exposure having a stronger explanatory power than the other two traits. Our findings provide a first model to interpret variation of wing-feather moult phenotypes in passerines, and outlines the relevance of season for passerine moult, suggesting a dynamic link between moult expression and plumage requirements

Moulting in the wrong season? A house sparrow replacing a significant part of its plumage in winter

Extra moult episodes in wild passerines have rarely if ever been documented. Here, we report a case of a possible extra moult episode in a House Sparrow Passer domesticus, a species with just one moult per annual cycle. This bird was captured in active and intense plumage growth in Barcelona on 15 February 2021, c. five months after it had been ringed whilst undergoing its post-juvenile moult. This possible extra moult episode involved all body tracts except the crural, all tail tracts, and most wing tracts except the underwing coverts, primaries, primary coverts and alula. We found no evidence that this plumage replacement was the final phase of an interrupted post-juvenile moult. Hypotheses that could explain this extraordinary plumage growth include a mutation affecting the endogenous rhythm of the bird, severe stress, endocrine disruption or a predation event. Although the replacement of the wing feathers was highly asymmetric, we interpret this case as an extra moult episode of unknown cause rather than plumage regrowth after accidental loss (e.g. by predation), given that this plumage growth was compatible with three characteristics of moult not expected during the replacement of accidentally lost plumage: (i) it affected the whole of the bird’s plumage, (ii) involved feathers such as the axillaries that are rarely exposed, and (iii) showed sequential rather than simultaneous feather growth