The INSTITUTE for BIRD POPULATIONS
MOLT AND PLUMAGE STUDIES
 
IDENTIFICATION GUIDE

Molt and Plumage Studies Program banner photo

Accurately assessing the age and sex of birds is essential for understanding their population dynamics. Some birds can be aged and sexed easily by plumage but many require close examination of molt-related characteristics. IBP Biologist Peter Pyle literally “wrote the book” on age and sex determination of North American birds – Identification Guide to North American Birds.

IBP researchers work with scientists all over the world to study live birds and museum specimens, and assist researchers working in the field of avian demographics. We are also interested in molt strategies of birds, how to name molts and plumages, and how molts have evolved from reptiles to ancestral birds to modern-day birds.

For more information about our work with molt and plumage, contact Peter Pyle.

 

The MAPS Bander’s reference, Identification Guide to North American Birds, Parts I and II by IBP’s Peter Pyle is available from Slate Creek Press.

 
Bird Photo
 
 
SELECTED PUBLICATIONS

Peer-reviewed Publications Authored by IBP Personnel

Pyle, P., and M. McPherson. 2017. Why so many white Eared Grebes?: Possible interactions among leucism, molt, and pollutants. Birding 49(10):58-65. PDF

Guallar, S.X., A. Ruiz-Sánchez, R. Rueda-Hernández, and P. Pyle. 2016. Molt strategies of ten Neotropical passerine species. The Wilson Journal of Ornithology 128:543-555. PDF

Pyle, P. 2016. Secondary aging criteria. Birding 48(2):28-32. PDF

Pyle, P., and M. Reid. 2016. Molts and plumages in Long-tailed and other jaegers: An "alternate" explanation for nonbreeding plumages? Western Birds 47:242–257. PDF

Pyle, P., D.L. Webster, and R.W. Baird. 2016. White-rumped dark storm-petrels in Hawaiian Island waters: The quandary of Leach's vs. Band-rumped storm-petrels throughout the world. Birding 48(1):58-73. PDF

Pyle, P., K. Tranquillo, K. Kayano, and N. Arcilla. 2016. Molt patterns, age criteria, and molt-breeding dynamics in American Samoan landbirds. The Wilson Journal of Ornithology 128:56–69. PDF

Clark, W.S., and P. Pyle. 2015. A recommendation for standardized age-sex class plumage terminology for raptors. The Journal of Raptor Research 49:513-517. PDF

Howell, S.N.G., and P. Pyle. 2015. Use of "definitive" and other terms in molt nomenclature: a response to Wolfe et al. The Auk: Ornithological Advances 132:365–369. PDF

Pyle, P., A. Engilis Jr., and D.A. Kelt. 2015. Manual for ageing and sexing landbirds of Bosque Fray Jorge National Park and north-central Chile, with notes on occurrence and breeding seasonality. Special Publications of the Louisiana State University. PDF

Pyle, P., A. Engilis Jr., and D.A. Kelt. 2015. Manual para estimar edad y sexo en aves del Parque Nacional Bosque Fray Jorge y Chile Central, con notas sobre rangos de distribución y estación reproductiva. Special Publications of the Louisiana State University. PDF

Pyle, P., R.J. Keiffer, J.L. Dunn, and N. Moores. 2015. The Mendocino shrike: Red-backed Shrike (Lanius collurio) x Turkestan Shrike (L. phoenicuroides) hybrid. North American Birds 69:4-35. PDF

Sealy, S.G., P. Pyle, and H.R. Carter. 2015. Ancient Murrelets molt flight feathers after the precocial young become independent. The Northwestern Naturalist 96:212-221. PDF

Guallar, S., A. Ruiz-Sánchez, R. Rueda-Hernández, and P. Pyle. 2014. Moult topography and its application to the study of partial wing-moult in two neotropical wrens. Ibis 156:311-320. PDF

McKee, T., P. Pyle, and N. Moores. 2014. Vagrancy and identification in first cycle Slaty-backed Gulls. Birding 46:38-51 plus 51A-J. PDF

Pyle, P. 2014. Plumages of second-basic and older Northern Harriers: a circular Circus? Birding 46:46-53. PDF

Rutt, C.L., P. Pyle, P.W. Collins, M.L. Brady, J.R. Tietz, and J.L. Dunn. 2014. The nominate subspecies of the Purple Finch in California and western North America. Western Birds 45:284–295. PDF

Nelson, K., and P. Pyle. 2013. Distribution and movement patterns of individual Crested Caracaras in California. Western Birds 44:45-55. PDF

Pyle, P. 2013. Dark-faced Common Murres off California in fall and winter. Western Birds 44:250-261. PDF

Pyle, P. 2013. Evolutionary implications of synapomorphic wing-molt sequences among falcons (Falconidae) and parrots (Psittaciformes). The Condor 115:593-602. PDF

Pyle, P. 2013. Harrier molts and plumages. Birding 45:10-12.

Pyle, P. 2013. Molt homologies in ducks and other birds: a response to Hawkins (2011) and further thoughts on molt terminology in ducks. Waterbirds 36:75-79. PDF

Junda, J., A.L. Crary, and P. Pyle. 2012. Two modes of primary replacement during prebasic molt of Rufous Fantails (Rhipidura rufifrons). The Wilson Journal of Ornithology 124:680-685. PDF

Ruiz-Sánchez, A., R. Rueda-Hernández, S. Guallar, and P. Pyle. 2012. Age determination of the Spot-breasted Wren and the White-breasted Wood-Wren using molt limits. North American Bird Bander 37:93-100. PDF

Wolfe, J.D., and P. Pyle. 2012. Progress in our understanding of molt patterns in Central American and Caribbean landbirds. In: Proceedings of the IX Neotropical Ornithological Congress-Peru. Ornitologia Neotropical 23:153-158. PDF

Wolfe, J.D., T.B. Ryder, P. Pyle, and E.I. Johnson. 2012. Using molt and plumage cycles to age tropical birds: updates and recent advances. Ornitologia Neotropical 23:153-158. PDF

Chambers, M., G. David, C. Ray, B. Leitner, and P. Pyle. 2011. Habitats and conservation of molt migrant birds in southeastern Arizona. The Southwestern Naturalist 56:204-211. PDF

De la Hera, I., D.F. DeSante, and B. Mila. 2011. Feather growth rate and mass in Nearctic passerines with variable migratory behavior and molt pattern. The Auk 129:222-230. PDF

Johnson, E.I., J.D. Wolfe, T.B. Ryder, and P. Pyle. 2011. Modifications to a molt-based ageing system proposed by Wolfe et al. (2010). The Journal of Field Ornithology 82:422-424. PDF

Pyle, P. 2011. Book review: Guallar et al., Paseriformes del Occidente de México: morfometría, datación y sexado. Revista Catalana d'Ornitologia 27:45-47. (Catalan Version) PDF

Pyle, P. 2011. Book review: Guallar et al., Paseriformes del Occidente de México: morfometría, datación y sexado. Western Birds 42:120-122. (English Version) PDF

Pyle, P. 2011. Nomenclature of the Laysan Honeycreeper, Himatione [sanguinea] fraithii. The Bulletin of the British Ornithological Club 131:116-117. PDF

Radley, P., A.L. Crary, J. Bradley, C. Carter, and P. Pyle. 2011. Molt patterns, biometrics, and age and gender classification of landbirds on Saipan, Northern Mariana Islands. The Wilson Journal of Ornithology 123:588-594. PDF

Wolfe, J.D., and P. Pyle. 2011. First evidence for eccentric prealternate molt in the Indigo Bunting (Passerina cyanea): possible implications for adaptive molt strategies. Western Birds 42:257-262. PDF

Chandler, R.M., P. Pyle, M.E. Flannery, D.J. Long, and S.G. Howell. 2010. Flight feather molt of Turkey Vultures. The Wilson Journal of Ornithology 122:354-360. PDF

Pyle, P., and R. Kayhart. 2010. Replacement of primaries during the prealternate molt of a Yellow Warbler. North American Bird Bander 35:178-181. PDF

Wolfe, J.D., T.B. Ryder, and P. Pyle. 2010. Using molt cycles to categorize the age of tropical birds: an integrative new system. The Journal of Field Ornithology 81:186-194. PDF

Pyle, P. 2009. Age determination and molt strategies in North American alcids. Marine Ornithology 37:219-225. PDF

Pyle, P., W.A. Leitner, L. Lozano-Angulo, F. Avilez-Teran, H. Swanson, E. Gómez-Limón, and M.K. Chambers. 2009. Temporal, spatial, and annual variation in the occurrence of molt-migrant passerines in the Mexican monsoon region. The Condor 111:583-590. PDF

Wolfe, J.D., P. Pyle, and C.J. Ralph. 2009. Breeding seasons, molt patterns, and gender and age criteria for selected northeastern Costa Rican resident landbirds. The Wilson Journal of Ornithology 121:556-567. PDF

Pyle, P. 2008. Birding by feather: a molt and plumage primer. Birding web extra. PDF

Pyle, P. 2008. Identification Guide to North American Birds, Part II. Slate Creek Press, Bolinas, CA. (Copies of this book can be ordered from Slate Creek Press, http://www.slatecreekpress.com/orderIDG.htm). Order

Pyle, P., S.L. Jones, and J.M. Ruth. 2008. Molt and aging criteria for four North American grassland passerines. U.S. Fish and Wildlife Service, Biological Tech. Pub., FWS/BTP-R6011-2008, Washington, D.C. PDF

LeValley, R., and P. Pyle. 2007. Notes on plumage maturation in the Red-tailed Tropicbird. Western Birds 38:306-310. PDF

Pyle, P. 2007. Revision of molt and plumage terminology in Ptarmigan (Phasianidae: Lagopus spp.) based on evolutionary considerations. The Auk 124:508-514. PDF

Pyle, P. 2006. Book review: E.M. McCarthy, Handbook of avian hybrids of the world. Western Birds 37:237-239. PDF

Pyle, P. 2006. Staffelmauser and other adaptive wing-molt strategies in larger birds. Western Birds 37:179-185. PDF

Howell, S.N.G., and P. Pyle. 2005. Molt, age determination, and identification of puffins. Birding 37:412-418. PDF

Pyle, P. 2005. First-cycle molts in North American Falconiformes. Raptor Research 39:378-385. PDF

Pyle, P. 2005. Molts and plumages of ducks. Colonial Waterbirds 28:207-218. PDF

Pyle, P. 2005. Remigial molt patterns in North American Falconiformes as related to age, sex, breeding status, and life-history strategies. The Condor 107:823-834. PDF

Howell, S.N.G., C. Corben, P. Pyle, and D.I. Rogers. 2004. The first basic problem revisited: a reply to commentaries on Howell et al. 2003. The Condor 106:206-210. PDF

Pyle, P., A. McAndrews, P. Veléz, R.L. Wilkerson, R.B. Siegel, and D.F. DeSante. 2004. Molt patterns, and age and sex determination of selected southeastern Cuban landbirds. The Journal of Field Ornithology 75:136-145. PDF

Pyle, P., and S.N.G. Howell. 2004. Ornamental plume development and the "prealternate molts" of herons and egrets. The Wilson Bulletin 116:287-297. PDF

Froehlich, D. 2003. Ageing North American landbirds by molt limits and plumage criteria: a photographic companion guide to the Identification Guide to North American Birds, Part I. Slate Creek Press, Bolinas, CA. PDF

Howell, S.N.G., C. Corben, P. Pyle, and D.I. Rogers. 2003. The first basic problem: a review of molt and plumage homologies. The Condor 105:635-653. PDF

Howell, S.N.G., and P. Pyle. 2002. Ageing and molt in nonbreeding Black-bellied Plovers. Western Birds 33:268-270. PDF

McKee, T., and P. Pyle. 2002. Plumage variation and hybridization in Black-footed and Laysan Albatrosses. North American Birds 56:131-138. PDF

Pyle, P., and S.N.G. Howell. 2000. Revised ageing and sexing criteria for the Blue-throated Hummingbird. North American Bird Bander 25:134-137. PDF

Pyle, P. 1999. Molts by age in the Bristle-thighed Curlew and other shorebirds. Western Birds 30:181-183. PDF

Pyle, P. 1998. Book Review: J.L. Dunn and K.L. Garrett, A field guide to the warblers of North America. Western Birds 29:233-234. PDF

Pyle, P. 1998. Eccentric first year molt patterns in certain Tyrannid flycatchers. Western Birds 29:29-35. PDF

Pyle, P., and P. Unitt. 1998. Molt and plumage variation by age and sex in the California and Black-tailed Gnatcatchers. Western Birds 29:280-289. PDF

Pyle, P. 1997. A further examination of wing and tail formulae in Contopus and Empidonax flycatchers. Pages 147-154 in: R.W. Dickman, editor. The Era of Allan Phillips: A Festschrift, Albuquerque, NM. PDF

Pyle, P. 1997. First year Slaty-backed Gull. Birders Journal 6:251. PDF

Pyle, P. 1997. Flight-feather molt patterns and age in North American owls. American Birding Association Monographs in Field Ornithology 2:1-32. PDF

Pyle, P. 1997. Molt limits in North American passerines. North American Bird Bander 22:49-89. PDF

Pyle, P., S.N.G. Howell, and G.M. Yanega. 1997. Molt, retained flight feathers, and age in North American hummingbirds. Pages 155-166 in: R.W. Dickman, editor. The Era of Allan Phillips: A Festschrift., Albuquerque, NM. PDF

Yanega, G.M., P. Pyle, and G. Geupel. 1997. The timing and reliability of bill corrugations for ageing hummingbirds. Western Birds 28:13-18. PDF

Pyle, P., and S.N.G. Howell. 1996. Intraspecific variation and the identification of Spizella sparrows. Birding 28:374-387. PDF

Ralph, C.J., G.R. Geupel, P. Pyle, T.E. Martin, D.F. DeSante, and B. Milá. 1996. Manual de métodos de campo para el monitoreo de aves terrestres. General Technical Report PSW-GTR-159. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. PDF

Pyle, P. 1995. Incomplete flight feather molt and age in certain North American non-passerines. North American Bird Bander 20:15-26. PDF

Pyle, P., and S.N.G. Howell. 1995. Flight-feather molt patterns and age in North American Woodpeckers. The Journal of Field Ornithology 66:564-581. PDF

Ralph, C.J.. G. Geupel, P. Pyle, T.E. Martin, and D.F. DeSante. 1993. Handbook of field methods for monitoring landbirds. U.S.D.A. Forest Service General Technical Report PSW-GTR-144. PDF

Pyle, P., and D. Sibley. 1992. Juvenal-plumed LeConte’s Sparrows on migration. Birding 24:70-76. PDF

Pyle, P., and P. Henderson. 1990. On separating female and immature Oporonis warblers in fall. Birding 22:222-229. PDF

Pyle, P. 1988. Comments and errata for Identification Guide to North American Passerines. North American Bird Bander 13:112-113. PDF

Pyle, P. 1987. Identification Guide to North American Birds. Part 1. Slate Creek Press, Bolinas, CA. (Copies of this book can be ordered from Slate Creek Press, http://www.slatecreekpress.com/orderIDG.htm).

Pyle, P., S.N.G. Howell, R.P. Yunick, and D.F. DeSante. 1987. Identification Guide to North American Passerines. Slate Creek Press, Bolinas, CA.

Pyle, P. 1985. Book review: L. Svensson, Identification Guide to European Passerines. North American Bird Bander 10:22-23. PDF

Peer-reviewed Publications by Other Researchers

Snyder, T.A. III. 2009. Molt strategies in Alaskan Arctic Warblers. North American Bird Bander 33:174-176. PDF

Other Publications and Reports

Pyle, P. 2012. Updated Manual for Ageing and Sexing Landbirds of American Samoa. The Institute for Bird Populations, Point Reyes Station, CA PDF

Pyle, P., P. Radley, J. Bradley, and C. Carter. 2008. Manual for ageing and sexing Saipanese birds, with notes on breeding seasonality. Commonwealth of the Northern Mariana Islands Division of Fishand Wildlife Research Program, Saipan, Northern Mariana Islands. The Institute for Bird Populations, Point Reyes Station, CA. PDF

The INSTITUTE for BIRD POPULATIONS