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Evidence of altitudinal moult-migration in a Central American hummingbird, Amazilia cyanura

Published online by Cambridge University Press:  11 October 2010

K. C. Fraser ,
A. W. Diamond  and
L. Chavarría
K. C. Fraser*
Affiliation:
Department of Biology, University of New Brunswick, Fredericton, P.O. Box 4400, E3B 5A3, Fredericton, New Brunswick, Canada
A. W. Diamond
Affiliation:
Department of Biology, University of New Brunswick, Fredericton, P.O. Box 4400, E3B 5A3, Fredericton, New Brunswick, Canada
L. Chavarría
Affiliation:
Finca y Reserva Silvestre Privada Nebliselva El Jaguar, P.O. Box Apartado E-22, Managua, Nicaragua
*
1Corresponding author. Email: fraserkev@gmail.com
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Extract

For birds, moulting is an energetically costly endeavour (Murphy & King 1991), the timing and location of which may be flexible and governed by local ecological factors (Pyle et al. 2009, Rohwer et al. 2005). Some species or individuals may pause during long-distance migration, or migrate specifically to moult (Greenberg et al. 1974, Pyle et al. 2009, Rohwer et al. 2005, 2008). This strategy may be most common when food abundance reaches a nadir at the end of the breeding period, promoting movement to areas where food is more plentiful and the energetic and nutritive demands of moult may be met more suitably (Rohwer et al. 2005). This pattern is exemplified by insectivorous songbirds breeding in temperate, western North America that pause on southward migration to moult amidst the food flush that occurs following heavy rains in the Mexican monsoon region (Pyle et al. 2009, Rohwer et al. 2005, 2009), or more rarely, migrate upslope after breeding to moult in more moist, productive areas at higher elevation (Butler et al. 2002, Greenberg et al. 1974, Rohwer et al. 2008, Steele & McCormick 1995). Such altitudinal migration may be much more common in the Neotropics where many species engage in seasonal shifts in elevation. Hypotheses proposed to explain this behaviour, however, have focused on links made between migration and a principally frugivorous or nectarivorous diet (Levey & Stiles 1992, Stiles 1985, 1988) and not on moult requirements or phenology. Fruit and nectar availability may vary seasonally over an elevational gradient, and birds may migrate in order to track peak abundances (Levey & Stiles 1992, Loiselle & Blake 1991). Hummingbirds may also track arthropod (particularly spider) abundance, but this possibility remains little explored (Cotton 2007, Stiles 1980).

Keywords

altitudinal migrationdietintratropical migrationNeotropical birdsNicaraguaresource trackingseasonality
Type
Short Communication
Information
Journal of Tropical Ecology , Volume 26 , Issue 6 , November 2010 , pp. 645 - 648
Copyright
Copyright © Cambridge University Press 2010

For birds, moulting is an energetically costly endeavour (Murphy & King Reference MURPHY and KING1991), the timing and location of which may be flexible and governed by local ecological factors (Pyle et al. Reference PYLE, LEITNER, LOZANO-ANGULO, AVILEZ-TERAN, SWANSON, LIMÓN and CHAMBERS2009, Rohwer et al. Reference ROHWER, BUTLER, FROEHLICH, Greenberg and Marra2005). Some species or individuals may pause during long-distance migration, or migrate specifically to moult (Greenberg et al. Reference GREENBERG, KEELER-WOLF and KEELER-WOLF1974, Pyle et al. Reference PYLE, LEITNER, LOZANO-ANGULO, AVILEZ-TERAN, SWANSON, LIMÓN and CHAMBERS2009, Rohwer et al. Reference ROHWER, BUTLER, FROEHLICH, Greenberg and Marra2005, Reference ROHWER, ROHWER and BARRY2008). This strategy may be most common when food abundance reaches a nadir at the end of the breeding period, promoting movement to areas where food is more plentiful and the energetic and nutritive demands of moult may be met more suitably (Rohwer et al. Reference ROHWER, BUTLER, FROEHLICH, Greenberg and Marra2005). This pattern is exemplified by insectivorous songbirds breeding in temperate, western North America that pause on southward migration to moult amidst the food flush that occurs following heavy rains in the Mexican monsoon region (Pyle et al. Reference PYLE, LEITNER, LOZANO-ANGULO, AVILEZ-TERAN, SWANSON, LIMÓN and CHAMBERS2009, Rohwer et al. Reference ROHWER, BUTLER, FROEHLICH, Greenberg and Marra2005, Reference ROHWER, HOBSON and ROHWER2009), or more rarely, migrate upslope after breeding to moult in more moist, productive areas at higher elevation (Butler et al. Reference BUTLER, DONAHUE and ROHWER2002, Greenberg et al. Reference GREENBERG, KEELER-WOLF and KEELER-WOLF1974, Rohwer et al. Reference ROHWER, ROHWER and BARRY2008, Steele & McCormick Reference STEELE and McCORMICK1995). Such altitudinal migration may be much more common in the Neotropics where many species engage in seasonal shifts in elevation. Hypotheses proposed to explain this behaviour, however, have focused on links made between migration and a principally frugivorous or nectarivorous diet (Levey & Stiles Reference LEVEY and STILES1992, Stiles Reference STILES, Diamond and Lovejoy1985, Reference STILES, Almeda and Pringle1988) and not on moult requirements or phenology. Fruit and nectar availability may vary seasonally over an elevational gradient, and birds may migrate in order to track peak abundances (Levey & Stiles Reference LEVEY and STILES1992, Loiselle & Blake Reference LOISELLE and BLAKE1991). Hummingbirds may also track arthropod (particularly spider) abundance, but this possibility remains little explored (Cotton Reference COTTON2007, Stiles Reference STILES1980).

From 2005 to 2010, we observed a common but little studied Central American endemic hummingbird (Amazilia cyanura, Gould 1859, blue-tailed hummingbird, 4.5 g) at our Nicaraguan study site (El Jaguar; 1350 m asl; 13°10′ N, 86°02′ W) during the wet season, but at no other time of year. An individual captured during mist-net monitoring at the site in 2005 was in flight-feather and body moult, but no indicators of local breeding were observed. Considering that El Jaguar sits atop the highest peaks in the region, and that most observations of Amazilia cyanura are on the Pacific coast near sea level (L. Chavarría pers. obs., M. Torrez pers. comm., Stiles & Skutch Reference STILES and SKUTCH1989), we presumed that individuals arriving at the study area were derived from lowland populations. We hypothesized that Amazilia cyanura may be a moult-migrant that moves from lower elevation to the study site to complete moult, but not to breed. The closely related, and better-studied A. saucerrottei (De Lattre & Bourcier 1846; steely-vented hummingbird), breeds from December to April in Costa Rica (Stiles & Skutch Reference STILES and SKUTCH1989). If we presume similar timing of breeding for Amazilia cyanura, then arrival at El Jaguar is consistent with migration following breeding. From 2007 to 2010 we expanded mist-netting efforts to determine more specifically the period of tenure and activity of Amazilia cyanura at the study site.

El Jaguar can be classified as lower-montane moist forest (Holdridge Reference HOLDRIDGE1967) and consists of mostly primary forest and second-growth (~80% of the site) as well as active coffee (Coffea spp.) plantation (~20%), shaded by banana, Musa acuminata. Capture effort was divided between the coffee plantation and adjacent forest. Birds were captured using 2–27 mistnets (12 × 2.5 m, 36-mm mesh). From October 2007 to May 2010, mistnetting took place for 2–6 d each month, except in April 2008, June 2009 and February 2010. All data collected from individuals in the field followed protocols outlined by Monitoreo de Sobrevivencia Inveranal (De Sante et al. Reference DE SANTE, SARACCO, DE VIVAR ALVAREZ and MORALES2009). Body moult was scored on a four-point scale (0 = none to 4 = heavy). Flight feather moult was recorded as absent or present (which included adventitious, symmetric or juvenile growth); which specific feathers were moulting was recorded for some captures. Fat was scored visually on a scale of 0 (none) to 7 (excess) based on estimates of amount of fat in the furcular region of each individual. Breeding indicators were assessed visually and recorded on a number scale (brood patch: 0 = none to 5 = new feathers growing in; cloacal protuberance: 0 = none to 3 = large). We were not able to distinguish older from younger adults as no published accounts of visual age indicators exist for Amazilia cyanura or a closely related species, but plumage characters would allow the identification of juveniles (Howell & Webb Reference HOWELL and WEBB1995).

We logged 12 968 cumulative net hours between October 2007 and May 2010 (Figure 1a), We captured 12 Amazilia cyanura between 22–23 May 2008, 8 between 12–13 May 2009, and three on 19 April 2010 (Figure 1b). We did not capture, or observe any Amazilia cyanura during the mist-netting bouts in any other months (June–March). In our pilot work for this project, we captured one Amazilia cyanura in July (2005) but from 2007 to 2010 we captured birds only in April and May. All individuals were caught in mist nets placed in the coffee plantation and no Amazilia cyanura was captured, or observed, in the adjacent forest. Although we captured many individuals of several hummingbird species smaller than 5 g, the mesh-size of the mist nets we used was large for birds of this size (36 mm). If this reduced our capture rate, our main results should not be affected, but it may preclude the use of our data for density estimates.

Figure 1. Netting effort (a) and captures (b) of Amazilia cyanura between October 2007 and May 2010 at 1350 m in north-western Nicaragua. Most captured individuals (22/23) were in active moult (91% in body moult, 74% in flight feather moult). No breeding activity has been observed at the capture site from 2004–2010.

Of the 23 individuals captured, 17 (74%) were in active flight feather moult and 21 (91%) were in active body moult. When time at the ringing station allowed, specific feather tracts in moult were noted; four birds were growing primary feathers and one was growing retrices. Of those in body moult, 17 (81%) were scored as ‘medium’ or ‘heavy’ moult. All birds captured had adult plumage (Howell & Webb Reference HOWELL and WEBB1995, Stiles & Skutch Reference STILES and SKUTCH1989). Most birds (68%) had fat scores of 1 (n = 9) or 2 (n = 4). We did not observe any indications of breeding such as nests, breeding displays or the capture of juveniles or recently fledged young. No captured birds had brood patches or cloacal protuberances, although these may not be reliable indicators of breeding activity in hummingbirds (Diamond Reference DIAMOND1974). We did not ring individuals so have no data on inter-year recaptures. Missing tail feathers (due to sampling for a related project) would have identified intra-year recaptures but we did not observe any.

Our data suggest that Amazilia cyanura moves upslope to high-elevation cloud forest in Nicaragua to moult, but not to breed. This is the first observation of a moult-migration strategy in a hummingbird. Our captures from 2007 to 2010, along with an earlier observation, suggest that Amazilia cyanura tenure at El Jaguar is from late April to mid-July. Despite 9730 h of trapping effort between August and March, we caught no Amazilia cyanura. It is unlikely that this species breeds while at El Jaguar, as we found no signs of breeding activity (capture of fledged young, nests or displays, brood patch or cloacal protuberance). No nests or breeding activity have been observed during fieldwork at this site since 2004 (L. Chavarría, unpubl. data). Future research may show whether Amazilia cyanura captured at El Jaguar originate, and possibly breed, in lowland areas along the Pacific coast where they are more commonly observed. Little is known about breeding activity in Amazilia cyanura and the nest of this species is undescribed (Howell & Webb Reference HOWELL and WEBB1995).

Most (68%) Amazilia cyanura individuals were carrying relatively large amounts of fat and yielded scores of one or two. For comparison, two other hummingbird species that spend the year in the El Jaguar study area carried less fat; in Campylopterus hemileucurus (Deppe 1830; violet sabrewing) 34% of captures had fat scores of 1 or 2; in Phaethornis longirostris (Delattre, 1843; long-billed hermit), 23% of captures had a score of 1 and 0% had a score of 2 (K. Fraser & L. Chavarría unpubl. data). Higher fat scores in Amazilia cyanura, as compared to known sedentary species, are consistent with patterns of fat deposition to support migration, but also patterns reported for hummingbirds in active moult (Stiles Reference STILES1980).

Determining which factors favour upslope migration and moult in Amazilia cyanura is an interesting area for future research. Unproductive late-summer breeding areas seem to favour moult migration in some North American insectivorous passerines, which delay moult until arrival in Mexican monsoon region or at higher elevation within the USA where more moist conditions support a higher abundance of arthropods (Pyle et al. Reference PYLE, LEITNER, LOZANO-ANGULO, AVILEZ-TERAN, SWANSON, LIMÓN and CHAMBERS2009, Rohwer et al. Reference ROHWER, BUTLER, FROEHLICH, Greenberg and Marra2005, Reference ROHWER, HOBSON and ROHWER2009). Tenure of Amazilia cyanura at El Jaguar coincides with the early rainy season, which generally corresponds to peak arthropod abundance and bird breeding activity in tropical forests (Poulin et al. Reference POULIN, LEFEBVRE and McNEIL1992). Hummingbirds, including Amazilia species, commonly moult in the mid-rainy season (Stiles Reference STILES1980) perhaps owing to the increased availability of arthropods. Amazilia cyanura and five other hummingbird species captured at the study site derive their feather protein principally from arthropods. Two of these species (Campylopterus hemileucurus and Phaethornis longirostris) consumed prey with higher protein concentration in the breeding and moulting period than in the non-breeding period (Fraser et al. unpubl. data) which emphasizes the seasonal importance of arthropods. An exploration of seasonal arthropod availability over an elevational gradient may yield insight into factors driving a moult-migration strategy in Amazilia cyanura.

Species that migrate seasonally over an elevational gradient may pose a particular challenge to conservationists, in that altitudinal migrants often make use of multiple habitat types over a broader geographical range than more sedentary species (Powell & Bjork Reference POWELL and BJORK1995, Winker et al. Reference WINKER, ESCALANTE, RAPPOLE, RAMOS, OEHLENSCHLAGER and WARNER1997). Amazilia cyanura, a Central American endemic, may require both suitable lowland habitat for breeding, as well as upland habitat for moulting. Further investigation may yield other altitudinal moult-migrants in this region.

ACKNOWLEDGEMENTS

Georges Duriaux, Moisés Siles, Oscar and Johnny Rodríguez, provided field assistance and we thank Wayne Arendt of the U.S. Forest Service and Cuentas Criticas Project for field support. We thank Meredith Clayden and Trina Du for sample preparation and Anne McGeachy and Christine Paton for their work at the SINLAB. Funding was provided by a NSERC post-graduate scholarship to KCF. We thank Emily McKinnon and four anonymous reviewers for their helpful comments on earlier drafts of this manuscript.

References

LITERATURE CITED

BUTLER, L. K., DONAHUE, M. G. & ROHWER, S. 2002. Molt-migration in Western Tanagers (Piranga udoviciana): age effects, aerodynamics, and conservation implications. The Auk 119:1010–1023.CrossRefGoogle Scholar
COTTON, P. A. 2007. Seasonal resource tracking by Amazonian hummingbirds. Ibis 149:135–142.CrossRefGoogle Scholar
DE SANTE, D. F., SARACCO, J. F., DE VIVAR ALVAREZ, C. R. & MORALES, S. 2009. Instructions for establishing and operating bird-banding stations as part of the MoSI program. Institute for Bird Populations, Pt. Reyes Station. 44 pp.Google Scholar
DIAMOND, A. W. 1974. Annual cycles in Jamaican forest birds. Journal of Zoology 173:277–301.CrossRefGoogle Scholar
GREENBERG, R., KEELER-WOLF, T. & KEELER-WOLF, V. 1974. Wood warbler populations in the Yolla Bolly Mountains of California. Western Birds 5:81–90.Google Scholar
HOLDRIDGE, L. R. 1967. Life zone ecology. Tropical Science Center. San José, Costa Rica. 206 pp.Google Scholar
HOWELL, S. & WEBB, S. 1995. A guide to the birds of Mexico and Northern Central America. Oxford University Press. Oxford. 851 pp.CrossRefGoogle Scholar
LEVEY, D. J. & STILES, F. G. 1992. Evolutionary precursors of long-distance migration: resource availability and movement patterns in Neotropical landbirds. American Naturalist 140:447–476.CrossRefGoogle Scholar
LOISELLE, B. A. & BLAKE, J. G. 1991. Temporal variation in birds and fruits along an elevational gradient in Costa Rica. Ecology 72:180–193.CrossRefGoogle Scholar
MURPHY, M. E. & KING, J. R. 1991. Nutritional aspects of avian moult. Acta XX Congressus Internationalis Ornithologici 20:2186–2193.Google Scholar
POULIN, B., LEFEBVRE, G. & McNEIL, R. 1992. Tropical avian phenology in relation to abundance and exploitation of food resources. Ecology 73:2295–2309.CrossRefGoogle Scholar
POWELL, G. V. N. & BJORK, R. 1995. Implications of intratropical migration on reserve design: a case study using Pharomachrus mocinno. Conservation Biology 9:354–362.CrossRefGoogle Scholar
PYLE, P., LEITNER, W. A., LOZANO-ANGULO, L., AVILEZ-TERAN, F., SWANSON, H., LIMÓN, E. G. & CHAMBERS, M. K. 2009. Temporal, spatial, and annual variation in the occurrence of molt-migrant passerines in the Mexican monsoon region. The Condor 111:583–590.CrossRefGoogle Scholar
ROHWER, S., BUTLER, L. K. & FROEHLICH, D. R. 2005. Ecology and demography of East-West differences in molt scheduling of Neotropical migrant passerines. Pp. 87–105 in Greenberg, R. & Marra, P. P. (ed.). Birds of two worlds: the ecology and evolution of migration. Johns Hopkins University, Baltimore.Google Scholar
ROHWER, S., HOBSON, K. A. & ROHWER, V. G. 2009. Migratory double breeding in Neotropical migrant birds. Proceedings of the National Academy of Sciences 106:19050–19055.CrossRefGoogle ScholarPubMed
ROHWER, V. G., ROHWER, S. & BARRY, J. H. 2008. Molt scheduling of western Neotropical migrants and up-slope movement of Cassin's Vireo. The Condor 110:365–370.CrossRefGoogle Scholar
STEELE, J. & McCORMICK, J. 1995. Partitioning of the summer grounds by Orange-crowned Warblers into a breeding grounds, adult molting grounds and juvenile staging areas. North American Bird Bander 23:52.Google Scholar
STILES, F. G. 1980. The annual cycle in a tropical wet forest hummingbird community. Ibis 122:322–343.CrossRefGoogle Scholar
STILES, F. G. 1985. Conservation of forest birds in Costa Rica: problems and perspectives. Pp. 141–168 in Diamond, A. W. & Lovejoy, T. E. (eds.). Conservation of tropical forest birds. International Council for Bird Preservation, Kings College, Cambridge.Google Scholar
STILES, F. G. 1988. Altitudinal movements of birds on the Caribbean slope of Costa Rica: implications of conservation. Pp. 243–258 in Almeda, F. & Pringle, C. M. (eds.). Tropical rainforests: diversity and conservation. California Academy of Sciences, San Francisco.Google Scholar
STILES, F. G. & SKUTCH, A. 1989. A guide to the birds of Costa Rica. Comstock Publishing Associates, Ithaca. 511 pp.Google Scholar
WINKER, K., ESCALANTE, P., RAPPOLE, J. H., RAMOS, R. A., OEHLENSCHLAGER, R. J. & WARNER, W. D. 1997. Periodic migration and lowland forest refugia in a “sedentary” Neotropical bird, Wetmore's Bush-Tanager. Conservation Biology 11:692–697.CrossRefGoogle Scholar
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Figure 1. Netting effort (a) and captures (b) of Amazilia cyanura between October 2007 and May 2010 at 1350 m in north-western Nicaragua. Most captured individuals (22/23) were in active moult (91% in body moult, 74% in flight feather moult). No breeding activity has been observed at the capture site from 2004–2010.