FEATURED PHOTO Identifying Juvenile Warblers The Fun Really Begins Here Peter Pyle • Bolinas, California • [email protected] Christine M. Godwin • Fort McMurray, Alberta • [email protected] Kenneth R. Foster • Fort McMurray, Alberta • [email protected] he Monitoring Avian Productivity and Survivorship (MAPS) other areas, are now available online (tinyurl.com/land-birds- TProgram is a continent-wide collaborative effort among re- vital and see DeSante et al. 2015). searchers and citizen scientists to assist the conservation In 2011 the Boreal MAPS Program was initiated in northeast- of birds and their habitats through bird banding (tinyurl.com/ ern Alberta to evaluate landbird demographic rates in reclaimed MAPS-banding). Since 1989, more than 1,200 MAPS banding habitats and other habitats subjected to varying levels of dis- stations, spread across North America, have recorded more than turbance relative to those in natural boreal forests (Foster et al. 2 million bird captures. MAPS data enable assessment of avian 2012). Few demographic data on landbirds have been collected demographic vital rates such as productivity, recruitment, sur- in the boreal forest (Wells 2011), making this program an im- vival, and intrinsic population growth, and these supplement portant contributor to understanding bird populations and vital other monitoring data by providing insights into what factors rates from local to continental scales. During July of our first drive avian population declines. For example, low productivity field season we began to catch recently fledged juvenile wood- indicates problems are occurring on breeding grounds whereas warblers (family Parulidae) in the mist nets. Frankly, we had a low survival suggests problems are occurring on winter grounds very difficult time, at first, with their identification. or during migration. MAPS data recently have been used in an important study documenting substantial long-term effects mong passerines, “juveniles” are birds in “juvenile plumage,” of West Nile virus on survivorship in North American birds Athe first pennaceous plumage (i.e., covered with standard- (George et al. 2015). Up to seven vital rates from MAPS data, for issue feathers with a shaft and barbs), acquired by nestlings and 158 landbird species within various conservation regions and kept for some period after fledging. For some reason, wood Featured Photo–Juvenile Palm Warbler. We thought at first that this might be a Cape May Warbler (see below) until we considered the tail pattern (right). The Palm Warbler is the only locally breeding species, other than the Black-and-white Warbler (see below), in which the white patches to the inner webs of the outer rectrices extend to the feather tips. The dark olive edging to the primaries and the dark soles of the feet are also of use for identifying juvenile Palm Warblers. Northeastern Alberta, July 14, 2013. Photos courtesy of © Boreal MAPS Program. 58 BIRDING • DECEMBER 2015 Members-only In this expanded online version of the article, we provide additional images of familiar warblers in their unfamiliar juvenile expanded content. plumages: a bonus gallery quiz of twelve species (see pp. 60–61) and correpsonding answers (pp. 62–67), plus additional discussion of two more species (pp. 68–69), all photographed by researchers with the Boreal MAPS Program in northeastern Alberta. warblers remain in juvenile plumage for a the primaries, and especially the pattern ton, New York. very short period compared to other pas- of the white spots on the rectrices. Ad- Curson, J., D. Quinn, and D. Beadle. 1994. New serines, as little as a week or less follow- ditional images of 12 familiar warblers World Warblers. Christopher Helm, London. ing fledging, before undergoing the pre- in their unfamiliar juvenile plumages DeSante, D. F., D. R. Kaschube, and J. F. Saracco. formative molt and then becoming “con- appear in the gallery on pp. 60–61, fol- 2015. Vital Rates of North American Land- fusing fall warblers.” Some individuals lowed by discussion of their identifica- birds (tinyurl.com/land-birds-vital). Institute begin the preformative molt even before tion and that of two other species. See for Bird Populations, Point Reyes Station. fledging! Birders encounter these birds if you can identify these warblers before Dunn, J. L. and K. L. Garrett. 1997. A Field Guide in July throughout American forests, but checking the answers! to Warblers of North America. Houghton Mif- the appearances of juvenile warblers are flin, Boston. not well covered in field guides, includ- Acknowledgments Foster K. R., C. M. Godwin, and P. Pyle. 2012. ing the specialty warbler guides by Dunn We thank the Boreal MAPS Program Monitoring avian productivity and survivor- and Garrett (1997) and Stephenson and banders, including E. Blackburn, J. ship in the oil sands region of northeastern Whittle (2014). However, Curson et al. Bosman, B. Carnes, G. Coulombe, R. Alberta, pp. 563–571 in: A. B. Fourie and M. (1994) do illustrate juveniles of some Dudgragne, B. Fried, S. Gray, E. Hentsch, Tibbett, eds. Mine Closure 2012. Australian species, and it must be noted that Chap- J. Johnston, C. Kelly, P. Lai, D. Maynard, Centre for Geomechanics, Perth. man (1914) provides impressively accu- L. McDonald, R. McLaughlin, K. Morgan, George, T. L., R. J. Harrigan, J. A. LaManna, D. rate written descriptions of wood-war- C. Murray, L. Parker, K. Prince, G. Rand, F. DeSante, J. F. Saracco, and T. B. Smith. blers in what we today refer to as their A. Rosien, L. Villamil, C. Wagner, and K. 2015. Persistent impacts of West Nile vi- juvenile plumage. As with all plumages Wetten, for their excellent work and for rus on North American bird populations. of birds, we have discovered quite a bit taking most of the images used for this Proceedings of the National Academy of of intraspecific variation in the juvenile article. Funding in support of this proj- Sciences–USA, Early Edition (tinyurl.com/ appearance of each species, which does ect was provided by Syncrude Canada, WNV-persist). not make matters any easier. Ltd., Hammerstone Corporation, Cana- Pyle, P. 1997a. Molt limits in North American The preformative molt in most North dian Natural Resources Limited, Cenovus passerines. North American Bird Bander 22: American warblers is partial, including Energy, ConocoPhillips Canada, Devon 49–90. all body feathers and secondary coverts Energy, Husky Oil Operations, Ltd., Im- Pyle, P. 1997b. Identification Guide to North but no flight feathers, that is, the prima- perial Oil, Ltd., Suncor Energy, TOTAL American Birds, Part 1. Slate Creek Press, ries, primary coverts, secondaries, and E&P Canada, Nexen Energy ULC, and Bolinas. rectrices (Pyle 1997a, 1997b). Thus, the the Oil Sands Developers Group. This is Stephenson, T. and S. Whittle. 2013. The flight feathers we see on juveniles are the Contribution no. 521 of the Institute for Warbler Guide. Princeton University Press, same ones that help us identify confusing Bird Populations. Princeton. fall warblers in formative plumage, and Wells, J. V. 2011. Boreal Birds of North America: A these differ only subtly—primarily in References Hemispheric View of Their Conservation Links shape, wear, and fading—from the flight Chapman, F. M. 1914. The Warblers of and Significance. University of California feathers of adults. It follows, then, that North America, second edition. Apple- Press, Berkeley. the best way to identify juvenile warblers is by looking at the flight feathers, in par- ticular patterns to the rectrices and the color of the edges of the primaries, sec- ondaries, and primary coverts. The color of the “soles of the feet” (technically, the toe pads) can also provide a clue. With these pointers in mind, we turn now to matter of actual juvenile war- blers. Our featured photo is of a Palm Warbler, identified as such by the dark soles of the feet, the dark olive edging to ABA.ORG/BIRDING 59 FEATURED PHOTO Can You Identify These Juvenile Warblers? Hint: Consider the Wings and Tail ANSWERS AND ANALYSES ON PAGES 6267 B A C D E F 60 BIRDING • DECEMBER 2015 H G J I K L All of these juvenile warblers were mist-netted by researchers with the Boreal MAPS Program in northeastern Alberta. ABA.ORG/BIRDING 61 FEATURED PHOTO Although the body plumage does not leave A| much of a clue as to this warbler’s identification, it is one of the easiest of our juveniles to identify based on the unique tail pattern, with white oval- shaped spots to all but the central pair of rectrices. Not only can we confirm this bird as a juvenile Magnolia Warbler by the tail pattern, but the extent of white in the tail allows us to sex it as a male. Note also the dull grayish-brown edging to the primaries; and, although the mark is not visible in this image, juvenile and older Magnolia Warblers have yellow soles to the feet. Northeastern Alberta; July 17, 2013. Photos courtesy of © Boreal MAPS Program. This species begins the preformative molt around B| or slightly before the fledging date, and the bright pattern of yellow around the eyes led us to believe that this was a Canada Warbler. However, juvenile Canada Warblers have gray edging to the primaries and brighter yellow feet both above and below. Thus, the green edging to the primaries and duller yellow feet (often restricted in this species to the soles), identify this as a juvenile Wilson’s Warbler. Northeastern Alberta; July 12, 2011. Photos courtesy of © Boreal MAPS Program. 62 BIRDING • DECEMBER 2015 As with juvenile Palm and Magnolia warblers, C| tail pattern, wing edging, and the color to the soles of the feet help identify this bird. It is a juvenile Cape May Warbler. The wing edging is a brighter olive–green than in Palm and other ex-Dendroica (Setophaga now) warblers, and the tail spots are restricted and do not reach the tips of the outer rectrices.