Moult Strategies Research Articles

Earliest evidence of avian primary feathermoult.

Feather moulting is a crucial process in the avian life cycle, which evolved to maintain plumage functionality. However, moulting involves both energetic and functional costs. During moulting, plumage function temporarily decreases between the shedding of old feathers and the full growth of new ones. In flying taxa, a gradual and sequential replacement of flight feathers evolved to maintain aerodynamic capabilities during the moulting period. Little is known about the moult strategies of non-avian pennaraptoran dinosaurs and stem birds, before the emergence of crown lineage. Here, we report on two Early Cretaceous pygostylian birds from the Yixian Formation (125 mya), probably referable to Confuciusornithiformes, exhibiting morphological characteristics that suggest a gradual and sequential moult of wing flight feathers. Short primary feathers interpreted as immature are symmetrically present on both wings, as is typical among extant flying birds. Our survey of the enormous collection of the Tianyu Museum confirms previous findings that evidence of active moult in non-neornithine pennaraptorans is rare and likely indicates a moult cycle greater than one year. Documenting moult in Mesozoic feathered dinosaurs is critical for understanding their ecology, locomotor ability and the evolution of this important life-history process in birds.

Mercury contamination is an invisible threat to declining migratory shorebirds along the East Asian-Australasian Flyway

Exposure to pollutants is a potentially crucial but overlooked driver of population declines in shorebirds along the East Asian-Australasian Flyway. We combined knowledge of moult strategy and life history with a standardised sampling protocol to assess mercury (Hg) contamination in 984 individuals across 33 migratory shorebird species on an intercontinental scale. Over one-third of the samples exceeded toxicity benchmarks. Feather Hg was best explained by moulting region, while habitat preference (coastal obligate vs. non-coastal obligate), the proportion of invertebrates in the diet and foraging stratum (foraging mostly on the surface vs. at depth) also contributed, but were less pronounced. Feather Hg was substantially higher in South China (Mai Po and Leizhou), Australia and the Yellow Sea than in temperate and Arctic breeding ranges. Non-coastal obligate species (Tringa genus) frequently encountered in freshwater habitats were at the highest risk. It is important to continue and expand biomonitoring research to assess how other pollutants might impact shorebirds.

Primary moult in the annual cycle of adult African Oystercatchers Haematopus moquini

African Oystercatchers Haematopus moquini are sedentary, intertidal foraging birds, range-restricted to Namibia and South Africa. Their annual cycle has two components: breeding and moult. The Underhill–Zucchini model estimated a primary moult duration of 154 days, and mean start and completion dates of 1 April and 2 September. Most eggs (90%) are laid between mid-November and mid-February; thus, on average, oystercatchers have 2–3 months between moult completion and egg laying. The completion date confirms an overlap between moult and the period of post-fledging dependence of juveniles on their parents. The 154-day primary moult duration spreads the energetic demands of feather production to cope with this overlap and with the fact that primary moult extends through winter when storms make intertidal areas inaccessible for days. There are approximately 50 quantitative studies of primary moult for migrant waders (suborder Charadrii); this is the third for a resident species. The other two species of resident waders studied are in south-eastern Australia: the Hooded Dotterel Thinornis cucullatus and Sooty Oystercatcher Haematopus fuliginosus. The Hooded Dotterel has one of the longest estimated moult durations (203 days) and its moult and breeding overlap. The annual schedules for the Sooty Oystercatcher and African Oystercatcher are similar, as is the estimated moult duration: 149 and 154 days, respectively. Preliminary studies of the primary moult of the Eurasian Oystercatcher H. ostralegus indicate the duration to be 100 days, which is two-thirds that of the two sedentary oystercatchers. This is likely a consequence of Eurasian Oystercatchers having migration and harsh winter conditions as additional components of their annual cycle, and thus a limited period for primary moult. This study was based largely on photographic records of African Oystercatchers in flight, with contributions by citizen scientists. We make two key conclusions: the need for more studies of the moult strategies of the Haematopidae and resident waders; and digital photography of free-ranging birds can be used to study primary moult.

The relationship of moult timing, duration and sequence to the aerial lifestyle of the Little Swift (Apus affinis)

Feather moult is an important and energy‐demanding avian life‐history trait that is necessary to maintain the function of the plumage by replacing abraded feathers with new ones. However, during moult, aerodynamic capacity is temporarily impaired by the reduction and shape change of the flight surface. Therefore, among aerial birds, adaptations may evolve to reduce this impairment. Here, we studied the timing, duration and sequence of the annual complete moult of adult Little Swifts Apus affinis in northern Israel by examining the plumage of 55 individuals monthly in their colony. Primary moult occurs over 191.7 ± 24.0 days, representing 52.5 ± 6.6% of the annual cycle, and overlaps with the breeding season, a rare occurrence among small Palaearctic bird species. In addition, primary moult duration was significantly affected by its timing such that individuals that started to moult later had a shorter moult duration than those that started to moult earlier. This relationship is most likely to be a result of the time available for moult, which is limited by breeding and also by the cold season and the expected decline in food availability. Moult overlap with breeding or cold seasons may involve energetic and functional costs. Our results indicate two strategies that appear sequentially: (1) a slow and long moult that largely overlaps with breeding, and (2) a shorter moult that overlaps less with breeding (both strategies avoid moulting during the cold season). Most Little Swifts (85.7%) moulted their rectrices in a centripetal sequence starting with the outermost pair of rectrices inward. This moult was later in relation to wing feather renewal and had almost no overlap with primary moult. Finally, we tested a method for non‐invasively monitoring moult of small species by collecting and sampling shed feathers without the need to capture the birds themselves, as has been successfully used for larger bird species. This work demonstrates the importance of aerodynamic considerations in the evolution of life‐history traits. Moult‐related aerodynamic costs may be an important evolutionary factor shaping moult strategy, including timing, duration and sequence, mainly among species, like swifts, that are highly dependent on their aerodynamic ability.

Molt strategy and delayed plumage maturation in the Lined Seedeater

Molt strategy and delayed plumage maturation in the Lined Seedeater

Moult terminology: Let's make it simpler!

An understanding of feather moult, an important process in the life cycle of birds, lags behind that of other avian life‐history events. This lag includes a lack of scientific attention, but surprisingly also a lack of basic knowledge regarding the moult strategy of many bird species. This situation is particularly astonishing in light of the fact that feathers are a unique characteristic of birds. Currently, there are two main terminology systems for describing moult: one life‐cycle‐based and one plumage‐based (H–P terminology). A survey conducted among 434 birdwatchers, bird‐ringers (banders) and ornithologists showed a significant difference in understanding of the two terminologies. Ornithologists studying moult, as well as editors and reviewers, are called upon to make use of, and encourage the use of, understandable moult terminology, as much as possible. Using more understandable terms and language may help a wider audience of amateurs, students and ornithologists to understand moult. Involvement of a wider audience may advance data collection and research of this important event in the avian life cycle.

Bioinspired Chiral Template Guided Mineralization for Biophotonic Structural Materials.

Nature provides numerous biomineral design inspirations for constructing structural materials with desired functionalities. However, large-scale production of damage-tolerant Bouligand structural materials with biologically comparable photonics remains a longstanding challenge. Here, an efficient and scalable artificial molting strategy, based on self-assembly of cellulose nanocrystals and subsequent mineralization of amorphous calcium carbonate, is developed to produce biomimetic materials with an exceptional combination of mechanical and photonic properties that are usually mutually exclusive in synthetic materials. These biomimetic composites exhibit tunable mechanics from "strong and flexible", whichexceeds the benchmark of natural chiral materials, to "stiff and hard", which is comparable to natural and synthetic counterparts. Especially, the biomimetic composites possess ultrahigh stiffness of 2GPa in their fully water-swollen state-a value well beyond hydrated crab exoskeleton, cartilage, tendon, and stiffest synthetic hydrogels, combined with exceptional strength and resilience. Additionally, these composites are distinguished by the tunable chiral structural color and water-triggered switchable photonics that are absent in most artificial mineralized materials, as well as unique hydroplastic properties. This study opens the door for a scalable synthesis of resilient biophotonic structural materials in practical bulk form.

Adult male birds advance spring migratory phenology faster than females and juveniles across North America.

Advances in spring migratory phenology comprise some of the most well-documented evidence for the impacts of climate change on birds. Nevertheless, surprisingly little research has investigated whether birds are shifting their migratory phenology equally across sex and age classes-a question critical to understanding the potential for trophic mismatch. We used 60 years of bird banding data across North America-comprising over 4million captures in total-to investigate both spring and fall migratory phenology for a total of 98 bird species across sex and age classes, with the exact numbers of species for each analysis depending on season-specific data availability. Consistent with protandry, in spring (n= 89 species), adult males were the first to arrive and immature females were the last to arrive. In fall (n= 98), there was little difference between sexes, but adults tended to depart earlier than juveniles. Over 60 years, adult males advanced their phenology the fastest (-0.84 days per decade, 95 CrI=-1.22 to -0.47, n= 36), while adult and immature females advanced at a slower pace, causing the gap in male and female arrival times to widen over time. In the fall, there was no overall trend in phenology by age or sex (n= 57), driven in part by high interspecific variation related to breeding and molt strategies. Our results indicate consistent and predictable age- and sex-based differences in the rates at which species' springtime phenology is shifting. The growing gap between male and female migratory arrival indicates sex-based plasticity in adaptation to climate change that has strong potential to negatively impact current and future population trends.

Molt Strategies by Age and Subspecies in the Willow Flycatcher

We clarify the molt strategies of the Willow Flycatcher (Empidonax traillii) by subspecies through the examination of 455 museum specimens. Most and typically all juvenile primary coverts are retained during the preformative molt in fall and winter, allowing yearlings to be distinguished from older birds from their first spring through their second fall. In addition to replacing the body feathers and some to (usually) all secondary coverts and tertials, the preformative molt can include no other remiges or rectrices (46% of specimens), all remiges and rectrices (33%), or some remiges in an “eccentric” sequence (21%). During the prealternate molt, replacement of upper wing coverts and tertials is much less extensive than in the preformative molt, varying from replacement of no feathers in 27% of specimens to replacing more than half of the median and greater coverts and all three tertials in other specimens. Both the preformative and the first prealternate molts are significantly more extensive in eastern E. t. traillii than in the three western subspecies (brewsteri, adastus, and extimus). The definitive prealternate molt is also significantly more extensive than the first prealternate molt in the western subspecies but not in traillii. These differences between traillii and the other subspecies may result from longer migration distances, hence more solar exposure on an annual basis, and different molt-strategy dynamics between eastern and western North American passerines, perhaps relating to preferences for moister habitats. Further investigation is needed on the timing of molts on the winter grounds and the extent of body-feather replacement during the prealternate molt.

Identifying the winter grounds of the recently described Barbary Reed Warbler (Acrocephalus baeticatus ambiguus)

The Iberian and North African populations of reed warblers have been described recently as a separate taxon, ambiguus, forming a sister clade to the Sahelian subspecies minor of African Reed Warbler Acrocephalus baeticatus. Although the breeding range of ambiguus has been identified, the migration strategy of its populations remained unknown. We deployed geolocators and sampled the innermost primary from breeding adults in Spain for stable hydrogen (δ2H) analyses and also analysed stable carbon (δ13C) and nitrogen (δ15N) isotopes in feathers collected in two reed warbler taxa (Acrocephalus scirpaceus and Acrocephalus baeticatus ambiguus) in Morocco, to identify the moulting and wintering sites of these populations. Ring recoveries, geolocator tracks and probabilistic assignments to origin from δ2H values indicate that Spanish ambiguus are likely to moult south of the Sahara and winter in West Africa, probably from Mauretania to southern Mali and Ivory Coast. Moroccan ambiguus, however, undergo post‐breeding moult north of the Sahara, and possibly then migrate to West Africa. With other populations of ambiguus breeding from Algeria to Libya and probably wintering further east in the Sahelian belt, the Barbary Reed Warbler can therefore be considered a trans‐Saharan migrant, with a post‐breeding moult strategy that varies between populations, and probably structured according to breeding latitude.

Ventral feathers contained the highest mercury level in brown booby (Sula leucogaster), a pantropical seabird species

Seabirds are extensively used as environmental biomonitors and feathers are among the most analyzed matrices because they are one of the main excretory pathways to detoxify the bird's body of environmental contaminants. Still, there is a variation in contamination level between the different feathers of seabird species, driven by diet and physiology, such as molt strategy and feather formation sequence. We measured total mercury (THg) concentration in different types of feathers (wing, tail, ventral and dorsal) of the same individual in adults and juveniles of brown boobies (Sula leucogaster) from the northern coast of Rio de Janeiro state, Brazil. Brown booby had higher mean THg concentration (μg.g−1 d. w.) in ventral (adults: 6.46 ± 1.19, 4.79 to 8.34; juveniles: 4.23 ± 0.60, 3.07 to 5.07) and wing (adults: 5.85 ± 1.10, 4.66 to 8.32; juveniles: 3.86 ± 0.54, 3.23 to 4.63), compared to dorsal (adults: 4.52 ± 1.33, 3.01 to 6.44; juveniles: 3.51 ± 0.19, 3.29 to 3.8) and tail feathers (adults: 2.94 ± 0.45, 2.32 to 3.46; juveniles: 2.8 ± 0.23, 2.45 to 3.08). This difference may be explained because feathers grow in a specific sequence during molts leading to different THg concentrations in each type of feather. Additionally, juveniles had significantly lower concentrations of THg than adults in all feather types, which may be explained by the shorter life span, leading to less time to bioaccumulate Hg in their body. It is essential to choose carefully which feather type is more suitable to be used as a biomonitor of THg contamination in a particular species. For brown boobies, we suggest the use of ventral feathers, which represent the highest Hg concentration, are easy to sample and do not impair the seabird's flight ability, although more studies are needed to replicate these results in other tropical seabirds species.

Defining moults in migratory birds: a sequence‐based approach

Two broad nomenclatures have emerged to describe moult strategies in birds, the ‘life‐cycle' system which describes moults relative to present‐day breeding and other life‐history events, and the Humphrey–Parkes (H–P) system which reflects the evolution of moults along ancestral lineages. Using either system, challenges have arisen defining strategies in migratory species with more than one moult per year. When all or part of two moults occur in non‐breeding areas, extra moults may fail to be recognized or they may have been discriminated temporally, whether feathers are replaced in fall, winter or spring. But in some cases feather replacement can span the non‐breeding period, and this has resulted in an inability to identify inserted moults and to compare moult strategies between species. Furthermore, recent analyses on factors influencing the extent of the postjuvenile or preformative moults have either confined this moult to the summer grounds or presumed that it can be suspended and resumed on winter grounds, which has lead to quite divergent results and interpretations. Evolutionarily, the timing, extent and location of moults show phenotypic lability whereas the sequence in which feathers are replaced is comparatively conserved. As, such, I propose defining moults on the basis of feather‐replacement sequences as opposed to timing or location of replacement, including strategies in which discrete moults can be suspended for migration and overlap temporally. I provide examples illustrating the functionality of a sequence‐based definition in three migratory North American passerines that can undergo feather replacement twice in non breeding areas, and I demonstrate how this system can effectively apply to moults in many other passerine and non‐passerine species. I recommend that authors studying the evolutionary drivers of moult strategies in migratory birds adopt a sequence‐based approach and to carefully consider replacement strategies both prior to and following autumn migration.

Evolutionary trade-off between male colouration and feather moult extent also indirectly determines female moult.

Males and females are often influenced by different selective forces, frequently resulting in diverging phenotypes, for example in colouration. Since an animal's colouration may strongly influence its fitness, causes and consequences of sexual dichromatism in birds could aid in understanding important factors affecting sexual and natural selection. Variation in plumage ornamentation may affect mate attraction or intraspecific antagonistic behaviour. In most passerines, body plumage colouration of juveniles is obtained through the process of feather moult. The number of moulted wing and tail feathers, which also influences the bird's appearance, may affect its fitness. Here, we show that body plumage colouration of male, but not female, passerines is correlated with the number of moulted wing and tail feathers in the early stage of the bird's life for both sexes. Thus, the extent of wing and tail moult in females is not modulated by the female's colouration and can prevent females from reaching their sex-specific optima. This result could be explained by high intersexual genetic correlations, which might make it impossible for the sexes to reach their own trait fitness optima. Our findings may indicate that species-specific, rather than sex-specific, internal correlations shaped bird moult strategy, an important avian life-history trait.

Body mass and geographic distribution determined the evolution of the wing flight-feather molt strategy in the Neornithes lineage

The evolutionary history of many organisms is characterized by major changes in morphology and distribution. Specifically, alterations of body mass and geographic distribution may profoundly influence organismal life-history traits. Here, we reconstructed the evolutionary history of flight-feather molt strategy using data from 1,808 Neornithes species. Our analysis suggests that the ancestral molt strategy of first-year birds was partial or entirely absent, and that complete wing flight-feather molt in first-year birds first evolved in the late Eocene and Oligocene (25–40 Ma), at least 30 Myr after birds first evolved. Complete flight-feather molt occurred mainly at equatorial latitudes and in relatively low body mass species, following a diversification of body mass within the lineage. We conclude that both body mass and geographic distribution shaped the evolution of molt strategies and propose that the evolutionary transition towards complete juvenile molt in the Neornithes is a novel, relatively late adaptation.

Clarification of molt strategies in three Empidonax flycatchers

We studied plumages and molt patterns of Yellow-bellied (Empidonax flaviventris), Least (E. minimus), and Alder (E. alnorum) flycatchers, primarily on the breeding grounds but with additional data from wintering grounds and a migration stopover site, in order to clarify our knowledge of molt strategies in these species. We determined that these 3 species have a similar overall molt strategy: (1) a partial-to-incomplete preformative molt begun on the breeding grounds, suspended over migration, and completed on the wintering grounds; (2) a limited-to-partial first prealternate molt on the wintering grounds that can overlap the final stages of the preformative molt; (3) a complete definitive prebasic molt begun on summer grounds and completed on wintering grounds; and (4) a limited-to-partial definitive prealternate molt that may overlap with the final stages of the prebasic molt. Our study clarifies previous terminologies and allows these molts to be interpreted in an evolutionary framework. We suggest that observed differences in molt extents among species may be linked to differences in wintering latitude and habitat. The broadleaf forest preferred by Yellow-bellied Flycatcher likely retains insect biomass later into the winter season than the scrub habitat preferred by Least Flycatcher, and this may promote more extensive preformative feather replacement in that species. The much more extensive preformative molt of Alder Flycatcher may be due to its wintering farther south, where there is greater annual solar exposure, perhaps resulting in higher rates of feather degradation. Our data also suggest that the extent of prealternate molt in these species may vary with proximate factors on the winter grounds affecting individuals, rather than body condition at the beginning of winter.

PREFORMATIVE MOLT EXTENT AND AGING AND SEXING CRITERIA FOR EIGHT HUMMINGBIRD SPECIES IN SOUTHEASTERN PERU

Little attention has been paid to molt and age criteria in hummingbirds despite the importance of molt and age to numerous behavioral and ecological questions. We examined age-based molt patterns and bill corrugations in eight species of lowland Amazonian hummingbirds. Molt strategies and rates of bill smoothing were similar to those of more well-studied North American species, with all species showing partial preformative molts (replacing only body feathers and some wing coverts and retaining all remiges and rectrices), and bill corrugations reducing to less than 10% of bill length in all species during the first annual cycle. Several species showed evidence of delayed maturation in males in regard to plumage characteristics or bill coloration.

Filoplume morphology covaries with their companion primary suggesting that they are feather-specific sensors

Abstract Do birds detect and respond to forces acting on feathers through filoplumes, which appear to be unique mechanosensory feathers? If filoplumes function as sensors, their morphology should covary with the morphology of their companion feather to better detect feather movements and position. We explore covariation in filoplumes and primaries across 5 species of birds that vary in body size, molt strategy, and the functional life span of their primaries (Green-winged Teal [Anas crecca], Ring-billed Gull [Larus delawarensis], Turkey Vulture [Cathartes aura], Red-tailed Hawk [Buteo jamaicensis], and Red-winged Blackbird [Agelaius phoeniceus]). Filoplumes never extended beyond the coverts and inserted immediately adjacent to the base of their companion primaries, positioning them to detect subtle changes in feather vibration or movement. Far more variation in filoplume number and morphology was due to species differences than to individuals or position in the wing. Across species, filoplume length and number increased with calamus length of primaries. In the 2 species with growing primaries, the number and length of filoplumes were only weakly associated with molting primaries, suggesting that filoplumes were not replaced when their companion primary was replaced. Further, filoplumes associated with a growing primary were not replaced synchronously, leaving others to sense primary position and movement. Finally, filoplume number and length were greatest in Red-tailed Hawks, a species that carries individual feathers for multiple years, but links between filoplume morphology and molt strategy await broader comparative studies. Taken together, the morphology of filoplumes and their replacement schedule relative to their associated primary suggests that they are sensors, capable of detecting subtle differences in the position and movement of their companion feathers.

Extent and symmetry of tail moult in Amur Falcons

Amur Falcons Falco amurensis undergo one of the most extreme migrations of any raptor, crossing the Indian Ocean between their Asian breeding grounds and non-breeding areas in southern Africa. Adults are thought to replace all their flight feathers on the wintering grounds, but juveniles only replace some tail feathers before migrating. We compare the extent and symmetry of flight feather moult in a large sample of Amur Falcons killed at communal roosts during two hailstorms in KwaZulu-Natal, South Africa in March 2019, shortly before their northward migration. Most adults had completed replacing their remiges, with only a few still growing 1–3 feathers (mainly secondaries), but most were still growing their tail feathers. Juveniles only replaced tail feathers. Moult typically was distal from the central rectrices, but 25% of adults and 1% of juveniles replaced the outer tail first, and a few individuals exhibited other moult patterns (simultaneous moult across the tail, or among the inner and outer feathers). These different moult strategies were independent of sex. Adults that replaced the outer tail first typically had replaced a greater proportion of the rectrices (mean ± SD; 0.81 ± 0.19) than adults starting from the central tail (0.17 ± 0.08). Proportionally fewer distal moulting adults were killed on 9 March than 21 March, resulting in the average proportion of rectrices replaced by adults decreasing between the two storm events from 0.52 ± 0.26 to 0.43 ± 0.23. By comparison, juvenile tail moult increased from 9 March (0.34 ± 0.18) to 21 March (0.40 ± 0.15). Overall, the probability of replacement for T1 was similar for adults (0.82) and juveniles (0.83), but adults were more likely to have replaced T2–6 (0.40–0.45) than juveniles (0.18 for T2 and 0.04–0.07 for T3–6). Asymmetry in tail moult was greater at T1 for adults (15%) than juveniles (10%), but asymmetry for T2 to T6 was greater in juveniles (3–10%) than adults (1–4%), especially given the greater probability of feather replacement in adults. Despite these differences, the degree of asymmetry was less than expected by random replacement across all rectrices in both age classes. Interestingly, moult tended to be more advanced on the left than right side of the tail. The extent of tail moult was correlated with body condition in adults and juveniles, suggesting that moult pattern might be used as an indicator of fitness in falcons.

Ecological and evolutionary significance of molt in lowland Neotropical landbirds

AbstractThe slow-paced life history of many Neotropical birds (e.g., high survival and low fecundity) is hypothesized to increase lifetime fitness through investments in self-maintenance over reproduction relative to their temperate counterparts. Molt is a key investment in self-maintenance and is readily shaped by environmental conditions. As such, variation in molt strategies may be a key mechanism underlying life-history trade-offs and adaptation to new environments. Here, we review molt strategies from a diversity of lowland Neotropical landbirds and examine how variation in molt strategies, characterized by differences in molt insertions, timing, extent, and duration contribute to life-history variation and adaptation to diverse ecological conditions. In addition to our synthesis, we present a case study to examine the relationship between home range size and duration of the definitive prebasic molt of a well-studied subset of Amazonian landbirds. Our results suggest a connection between prolonged molt duration and larger home range size of small-to-medium-sized Amazonian landbirds. Our aims were to identify key gaps in our knowledge of Neotropical bird molt, to stimulate further comparative studies into the evolution of molt strategies, and to highlight how variation in molt strategies may be a key mechanism underlying life-history variation across latitudes.

Evolution of the preformative molt in Cardinalidae correlates with transitions from forest to open habitats

Abstract We explored adaptive factors affecting the preformative molt in the passerine family Cardinalidae, and concluded that the ancestor inhabited forest habitats and underwent a partial preformative molt that included wing coverts but not primaries. Later radiations within the family appeared to be characterized by transitions from forests toward more open habitats, and such transitions also correlated positively with increased preformative molt investment, plumage signaling, and flight. While previous studies had highlighted the role of time and energy constraints in the evolution of the preformative molt in passerines, we conclude that adaptation to the physical environment has had a greater influence than constraints on the evolution of this molt in Cardinalidae. Using molt data from 430 individuals from 41 of the 51 Cardinalidae species, we tested whether social and environmental factors (delayed plumage maturation and habitat openness), as well as that of physiological and time constraints (body mass, migration distance, and breeding latitude), have influenced the evolution of the preformative molt in this family. We predicted that these five factors could relate to the extent of the preformative molt in terms of energy investment, plumage signaling, and flight. We also examined whether or not the presence of an auxiliary preformative molt correlated to the extent of the preformative molt. We found a strong phylogenetic signal for the preformative molt in Cardinalidae due to shared ancestry, with habitat openness correlating significantly with increased molt extent. We also found a very strong relationship with the auxiliary preformative molt, indicating that both episodes form part of the early life molt strategy in this family. Evolutionary histories and the environments to which each taxonomic group has adapted can diverge across passerines, and we expect that future studies will further discover the nature and strength of the evolutionary drivers of preformative molt.