Moult Of Rectrices Research Articles

Second Prebasic Molt of a Black-headed Gull at Anchorage, Alaska

A second-cycle Black-headed Gull (Chroicocephalus ridibundus), a rare to casual visitor in western North America, remained at Anchorage, Alaska, from 16 July through 17 September 2023, providing a unique opportunity to track and document most stages of its second prebasic molt into definitive (adult) basic plumage. I estimated that the Anchorage bird required approximately 3 to 3.5 months (early/mid-June through late September) to complete the molt of its primaries. This is notably longer than the “average” 2.5 months stated for second-cycle Black-headed Gulls in several publications, but consistent with the duration and calendar limits reported by others for the entire species (mid-May/June through September). The start and duration of rectrix molt relative to the stage of primary molt closely matched that described for gulls in general, and specifically for predefinitive Bonaparte’s (C. philadephia) and Western (Larus occidentalis) gulls. When first observed in mid-July, the Anchorage bird had a white tail, as in definitive plumage, a trait infrequent in first-cycle Black-headed Gulls; then it molted the tail again through August. Although Black-headed Gulls occurring in western North America have been presumed to originate from eastern Asia, the timing of the Anchorage bird’s primary molt closely matched that published for second-cycle Black-headed Gulls in Europe, which has reported to be earlier—though molt schedules of Charadriiformes at the population level are highly variable.

Ecology of Gamebirds in Namha National Protected Area, Lao People’s Democratic Republic

Using camera-trap data, we describe the ecology and occupancy of several species of gamebirds while assessing associations at Namha National Protected Area (Lao People’s Democratic Republic). We detected three species of Arborophila Partridges, albeit in low numbers. Red Junglefowl Gallus gallus show typical diurnal activity, and we provide a record of a male–female pair commensally associated with a boar Sus scrofa. Silver Pheasants Lophura nycthemera have sex ratios slightly favoring females, and are mostly solitary; we provide novel findings of male age structure and rectrix molt. Gray Peacock Pheasants Polyplectron bicalcaratum sex ratios also favor females; males are recorded displaying as early as late February, while daily activity is somewhat bimodal, and we provide novel findings of male age structure. Analysis of the association between occupancy and 14 environmental covariates indicated that Silver Pheasant and Gray Peacock-Pheasant were associated with rougher terrain, and Red Junglefowl had higher occupancy far from well-groomed trails used for tourism. We discuss our results by comparing and contrasting our findings with other studies, and consider implications for conservation in the region.

High-intensity flight feather molt and comparative molt ecology of warblers of eastern North America

Abstract Rapid high-intensity molt of flight feathers occurs in many bird species and can have several detrimental consequences, including reductions in flight capabilities, foraging performance, parental care, and plumage quality. Many migratory New World warblers (family Parulidae) are known to have intense remigial molt, and recent work has suggested that simultaneous replacement of the rectrices may be widespread in the family as well. However, the phylogenetic distribution of simultaneous rectrix molt, and high-intensity flight feather molt more generally, has not been systematically investigated in warblers. We addressed this issue by examining flight feather molt in 13 species, representing 7 different warbler genera, at Powdermill Avian Research Center in southwestern Pennsylvania, USA. All 13 species replaced their 12 rectrices simultaneously, with the onset of rectrix molt occurring in the early-middle stages of high-intensity primary molt. As expected, single-brooded early migrants molted earlier than double-brooded species whose nesting activities extend into late summer. However, our finding that late-molting species replaced their primaries more slowly and less intensively than early molting species was unexpected, as late-molting species are widely hypothesized to be under stronger migration-related time constraints. This surprising result appears to be at least partially explained by a positive association between the pace of molt and daylength; shorter late-summer days may mandate reduced daily food intake, lower molt intensity, and a slower pace of molt. In comparison to other passerines, flight feather molt in warblers of eastern North America is extraordinarily intense; at its peak, individuals are simultaneously replacing 50–67% of their 48 flight feathers (all 12 rectrices and 6–10 remiges on each wing) for 2–3 weeks or more. Because molt of this intensity is likely to present numerous challenges for flight, avoiding predators, foraging, and parental care, the period of flight feather molt for warblers constitutes a highly demanding phase of their annual cycle.

The trade-off between molt and parental care in Hooded Warblers: Simultaneous rectrix molt and uniparental desertion of late-season young

ABSTRACT Temporal overlap between parental care and molt occurs frequently in birds, but few studies have examined how individuals manage conflicts between these 2 demanding phases of the annual cycle. The potential for trade-offs between molt and parental care is especially high in the Hooded Warbler (Setophaga citrina) because (1) all rectrices are replaced simultaneously during primary molt, leaving birds temporarily without a functional tail; and (2) the tail plays an important role in foraging, as birds use their white tail spots and tail-flicking behavior to startle insect prey. I examined how simultaneous rectrix molt affected late-season parental care in a color-banded population of Hooded Warblers in northwest Pennsylvania, USA. Of 62 adults initiating rectrix molt before the end of parental care, 43 (69%) deserted their late-season nestlings and fledglings, leaving the mate to provide all remaining parental care. Because females initiate rectrix molt significantly later than males, most instance...

Demographic variation in timing and intensity of feather molt in migratory Fork‐tailed Flycatchers (Tyrannus s. savana)

Understanding the annual cycle of migratory birds is imperative for evaluating the evolution of life-history strategies and developing effective conservation strategies. Yet, we still know little about the annual cycle of migratory birds that breed at south-temperate latitudes of South America. We aged, sexed, and determined the progression and intensity of body, remige, and rectrix molt of migratory Fork-tailed Flycatchers (Tyrannus s. savana) at breeding sites in southern South America and at wintering sites in northern South America. Molt of both body and flight feathers occurred primarily during the winter. In early winter, a similar proportion of young and adult flycatchers molted remiges and rectrices, but remige molt intensity (number of remiges molting) was greater and primary molt progression (mean primary feather molting) more advanced in adults. In late winter, remige molt intensity and primary molt progression did not differ between age groups. We found no difference between males and females either in the proportion of individuals molting in winter or in the intensity or progress of remige molt. Our results suggest that the nominate subspecies of Fork-tailed Flycatcher undergoes one complete, annual molt on the wintering grounds, and represents the first comprehensive evaluation of molt timing of a migratory New World flycatcher that overwinters in the tropics. Given that breeding, molt, and migration represent three key events in the annual cycle of migratory birds, knowledge of the timing of these events is the first step toward understanding the possible tradeoffs migratory birds face throughout the year. © 2016 Association of Field Ornithologists.

Pattern of Post-Juvenile Moult in Common Snipe (Gallinago Gallinago) and Its Implications for Ageing of the Species

External ageing of Common Snipe (Gallinago gallinago) still engenders considerable problems. To improve precision of age determination on the basis of plumage characteristics a scheme of post-juvenile moult was investigated in approximately 1200 first-year Common Snipes caught during autumn migration in central Poland. Post-juvenile moult was commenced from body feathers followed by moult of rectrices, lesser/median wing coverts and tertials. Moult sequence showed high inter-individual variability and was started in rectrices (36.9%), wing coverts (25.3%), tertials (8.4%) or simultaneously in several of these tracts of feathers (29.4%). Moult of rectrices was finished before completion of moult of wing coverts and tertials. Moult of tertials finished as the last from all age-indicative tracts of feathers. Consequently, tertials were suggested as the most useful for ageing of first-year Common Snipes in an advanced stage of moult. There was no case of moult of the outermost tertial in first-year birds. The second tertial from distal side of wing was moulted as the last one within this tract of feathers and thereby should be of special interest during plumage examination.

A PRIMER ON SUMMARIZING MOLT DATA FOR FLIGHT FEATHERS

Abstract Once established with reliability, the rules of flight feather replacement become an important component of comparative life-history studies. Here I illustrate the form of tables that should be used to describe the pattern and intensity of flight feather molt. Using a subset of original data summarizing primary, secondary, and rectrix molt in Western Kingbirds (Tyrannus verticalis), I show how to assign scores indicating direction of replacement and points where waves of molt started or will stop. Combining these scores across birds yields a molt summary table, the starting point for determining the rules of feather replacement. This raw summary table is then iterated to show breaks between molt series and how summary scores around these breaks are reassigned to acknowledge series breaks. Molt summary tables also give sample sizes, because the rules of flight feather replacement cannot reliably be inferred unless birds in active molt are available for all the feathers being considered.

An Unusual Sequence of Flight-Feather Molt in Common Murres and Its Evolutionary Implications

-Common Murres (Uria aalge) exhibit an unusual molt sequence. Primary molt begins at a focus between P4 and P7 and progresses in two rapid concurrent waves, proximally to P1, and distally to P10. The only other birds known to have a similar molt sequence are caracaras and falcons (Falconidae), parrots (Psittaciformes), and Pied Kingfishers (Ceryle rudis). Great Auks (Pinguinus impennis) also appear to have followed the same primary-molt sequence. Phylogenies for the Alcidae indicate that Great Auks, Common Murres, Thickbilled Murres (Uria lomvia), Razorbills (Alca torda), and Dovekies (Alle alle) share a common ancestor and are more closely related to one another than to other alcids. This suggests that the unusual sequence of primary molt in Common Murres is a shared-derived character that occurs in the other four species in their clade but has been overlooked. Adult male Common Murres have significantly shorter secondaries and longer primaries, on average, than do adult females, resulting in a slightly higher aspect ratio in males. Secondary molt begins when primary molt is more than one-third completed. Secondaries are replaced rapidly but sequentially (not synchronously or simultaneously); molt appears to proceed from two foci, proximally from S1 to S4, and both proximally and distally from S8, but more data are needed to clarify this point. Rectrix molt begins when primary molt is two-thirds completed. Rectrix loss and replacement occur rapidly, possibly synchronously, and in no apparent order. Adults molt about two weeks later than nonbreeding subadults. We found no differences in the timing of molt between the sexes in adults or subadults. Duration of flight-feather molt can vary from less than 25 days to more than 80 days, possibly reflecting interyear variation in prey abundance. Received 12 February 1997, accepted 9 December 1997. RELATIVE TO MOST OTHER TOPICS in ornithology, virtually all aspects of the molting process are poorly documented and understood (Pyle et al. 1987, Jenni and Winkler 1994). This is especially true in seabirds because most species, including all species that become flightless during molt, undergo molt at sea during the nonbreeding season (Palmer 1962, Glutz von Blotzheim and Bauer 1982, Cramp 1977, 1983, Warham 1996). Among alcids, molt has been better studied in Common Murres (Uria aalge) than in many other species (Verwey 1922, 1924, Salomonsen 1944, Stresemann and Stresemann 1966, Birkhead and Taylor 1977), but many aspects of their molt remain poorly known (contra Harris and Wanless 1990). As an extension of studies on seabird entanglement in gill nets in Puget Sound (Thompson et al. 1998), we studied molt in Common 4E-mail: thompcwt@dfw.wa.gov Murres. The phenology of breeding in Common Murres differs by two months or more among geographic areas. Thus, flight-feather molt scores in postbreeding adults might be useful for identifying breeding location (e.g. Oregon vs. Washington); this is important for determining the demographic effect of mortality caused by gill nets or other anthropogenic activities on different breeding populations of Common Murres. MATERIALS AND METHODS In 1993, commercial gill net fisheries occurred for summer sockeye salmon (Onchorhynchus nerka) in northern Puget Sound and for fall chum salmon (0. keta) in Hood Canal and central Puget Sound, Washington (Pierce et al. 1994). To evaluate various modified gill net designs, test fisheries were done in 1993 by Washington Sea Grant, and in 1993 and 1996 by Washington Sea Grant and Washington Department of Fish and Wildlife. Entangled seabirds were collected: (1) from commercial fisheries in 1993 from 1

Intraspecific and Interspecific Variation in Molt Patterns of Some Tropical Hummingbirds

Sequences of flight-feather replacement were determined for 13 species of Costa Rican hummingbirds based upon capture-recapture data for 5 to 60 individually marked, adult individuals per species. A single sequence of primary molt occurred in 99% of all individuals, proceeding from innermost to outermost, except that the three outermost primaries molted in the sequence 8-10-9. For secondaries and rectrices, molt typically commenced with the innermost and/or outermost feathers and proceeded centripetally, but with much individual variation. Between 2 and 18 different sequences were observed in these tracts for the different species, the number of sequences per species being closely correlated with the number of molt records. Each species showed two or three common sequences and various rare ones; within at least one species, some individuals showed different sequences in successive annual molts. It is incorrect to postulate genetically fixed, rigid sequences of at least secondary and rectrix molt for these species, or even for individuals within a species. Bilateral asymmetry of feather replacement was very rare for primaries, but more frequent for secondaries and rectrices. For five species in which at least 30 records were available, the progress of molt over the entire plumage was examined, using primary molt as a standard. Molt in secondaries and rectrices commenced when four to six primaries had been replaced, and finished at about the same time as did primary molt. Wing and tail coverts commenced molt after, and finished before, the primaries. In all species, body molt proceeded continuously throughout the period of primary molt, with minor differences in timing in different tracts being far exceeded by individual variation. The major difference between species occurred in the timing of the molt of the throat and crown-forehead. The more specialized and differentiated were these areas into glittering crowns, frontlets and/or gorgets, the later they molted. Females of sexually dichromatic species, although lacking the glittering plumage of their males in these areas, nevertheless showed delays in head molt nearly or quite as great as those shown by males.

Plumage and Molt in Shorebirds Summering at Enewetak Atoll

Abstract Various features of plumage and molt were studied in Golden Plovers, Whimbrels, Bristle-thighed Curlews, Wandering Tattlers, and Ruddy Turnstones. Specimens collected during July 1973 at Enewetak Atoll, Marshall Islands, represent birds that had not migrated to the northern breeding grounds. Based upon several criteria (bursa of Fabricius, wear of remiges and rectrices, and the condition of body feathers) most specimens appeared to be first-year birds. The relative development of alternate plumage showed considerable individual variation, which presumably reflects physiological variability in the factors controlling prealternate molt in the late winter and spring. Many birds remain in nonbreeding plumage (exhibiting only a few alternate feathers), and essentially pass from one basic plumage to another while on the winter range. Plovers replace primaries, secondaries, and some tertials during the winter, and were undergoing a complete prebasic molt in July. Such a pattern varies considerably from molt chronology in postnuptial adults. Whimbrels and Bristle-thighed Curlews finish wing molt in the late spring to midsummer, and birds collected in July had not yet begun prebasic molt. Wandering Tattlers were molting juvenal remiges commencing with the 6th and progressing to the 10th primary. The molting sequence of primaries 1 through 5 was not entirely clear. Museum skins indicated that remige molt starts with the 1st primary in some specimens. The overall pattern awaits detailed study for clarification. No indications of prebasic molt were found in summering turnstones, hence subsequent timing of this molt may coincide with that of postnuptial adults. As no wing molt was occurring, first-year birds apparently retain their juvenal remiges until the prebasic II molt. In each species, summering birds showed considerable individual variability in ongoing rectrix molt. Also some specimens had replaced a few or all of these feathers during the preceding winter while others had not.

Moult of the Red-Necked Stint

Timing and duration of moult of the Red-necked Stint are analysed from specimens collected at the southern limit of the winter range. The mean duration of primary moult is 110–115 days, starting between late August and early December and finishing between mid-December and late March. Secondary moult finishes before primary moult is completed, but moult of rectrices may not finish until shortly after. Thus, moult of the flight feathers coincides with the time spent on the wintering grounds. Pre-basic moult starts before birds arrive on the wintering grounds, and pre-alternate body-moult finishes after they leave. Moult of flight feathers does not start until the pre-basic moult is well advanced and does not finish until after the pre-alternate moult has started. Body-moult may be suspended during migration.