No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
GPS Telemetry Reveals Occasional Dispersal of Wood Storks from the Southeastern US to Mexico
Abstract
Mycteria americana (Wood Stork) is an iconic wading bird whose range includes Latin America and the southeastern US, where it is federally listed as threatened. Wetlands in the Gulf Coast states are used as post-breeding grounds by some individuals from both the US and the Mexican/Central American populations, and Wood Storks observed east and west of the Mississippi River Basin are generally thought to originate from the southeastern US and Mexico/Central America, respectively. In the context of a large-scale GPS telemetry study (133 individuals tracked over 14 years), we report the case of 2 Wood Storks that moved from Georgia and eastern Mississippi, respectively, to Mexico. One of the storks dispersed to Mexico as a juvenile and remained there for the subsequent 4 years into adulthood, indicating permanent settlement. Our findings provide evidence of potential mixing between the US and Mexican/Central American populations. These movements suggest that mixing between these Wood Stork populations, although probably sporadic, may be a more complex phenomenon than previously thought. While infrequent mixing may still have relevant consequences for gene flow between populations, such low levels of dispersal would most likely not be sufficient to support population replenishment from Mexico/Central America to the US or vice-versa.
... Si los humedales son hábitats y fuentes de alimento para las aves, ¿por qué estos sitios no se conservan a pesar de que existen programas que promueven su conservación y rescate? Es necesario que la sociedad conozca la importancia de estos ecosistemas para la avifauna local y migratoria, estas últimas lo utilizan en algunas temporadas o épocas del año cuando migran a la península de Yucatán evadiendo el invierno del hemisferio norte, buscando refugios y fuentes de alimento, tal como la cigüeña (Mycteria americana) quien es un ave migratoria proveniente del sur de los Estados Unidos que tiende a alimentarse de algunos moluscos y percharse para descansar en árboles de jícara o huiro (Crescentia cujete L.) (Drago y Lunaschi 2008, Picardi et al. 2018). ...
Los humedales son cuerpos de agua que proporcionan múltiples
beneficios ecosistémicos para la flora y fauna que los habita,
tanto como para humanos, debido a que proveen de agua que abastecen al manto freático. Sin embargo, estos ecosistemas se
encuentran fuertemente amenazados por diferentes actividades
antropogénicas, los cuales ponen en riesgo su equilibrio ecológico. Además, funcionan como zonas de alimentación y refugio para grupos particulares, como la avifauna, que depende de estos lugares para subsistir. Por tal razón, es necesario continuar documentando su diversidad para que los humedales estuarinos, continentales y temporales también puedan ser considerados como áreas prioritarias de conservación de flora y fauna.
... Movement ecology has primarily been studied in stork species with confirmed migratory movements (e.g., Abdim's Stork, C. abdimii : Jensen et al., 2006;Oriental Stork: Shimazaki et al., 2004;Yang et al., 2021;White Stork: Chernetsov et al., 2004;Rotics et al., 2016;Flack et al., 2016;Black Stork: Bobek et al., 2008;Literák et al., 2017), although the Wood Stork in the USA is a notable exception (Borkhataria et al., 2013;Bryan et al., 2008;Picardi et al., 2018). More limited telemetry research has also been conducted on the Asian Openbill in Thailand (Ratanakorn et al., 2018), and there has been one postgraduate study on Jabiru (Jabiru mycteria) movement in Belize that was not subsequently published and, therefore, not included in our literature search (Figueroa, 2005). ...
Storks are a conspicuous pan-global freshwater flagship taxon with 20 extant species, all of which have been accorded IUCN Red List status. Red List assessments use a combination of scientific evidence and expert inputs to develop species-level status, but there is little careful evaluation of whether these assessments are comparable across species. Using standard literature databases, we compiled and analysed patterns of research in peer-reviewed literature for all 20 stork species. Our search yielded 989 publications between 1950 and 2022, showing bias in both the coverage of species (66 % covered three stork species) and geographical locations (53.8 % from Europe and the United States of America) despite the highest stork species richness being present in Africa and Asia. Publications on storks, especially from Asia, have increased over time, with 81 % of all studies published since 2000. Most stork research focused on breeding ecology, but was skewed toward only three species. Growing research in Asia showed significant populations of several stork species amid farmlands, suggesting the need to advance similar research in anthropogenically modified landscapes elsewhere. The population and behaviour ecologies of 15 (75 %) stork species remain unstudied. Our review showed scientific evidence varying enormously across stork species, with sparse scientific understanding being the norm. Red List statuses must be made more robust for storks, especially highlighting data-deficient species to help prioritize conservation research, particularly in Africa and Asia, thereby facilitating the development of accurate status assessments for these species.
... Indication that movements between different areas within the range are repeated year after year, thus presenting typical migration features, was provided by a study on juveniles (Hylton 2004). Other tracking studies have described fine-scale movements (Borkhataria et al. 2013) or dispersal (Bryan et al. 2008, Picardi et al. 2018), but not migration. Overall, we lack a formal understanding of the migratory status of the wood stork population. ...
The function of migration is to allow exploitation of resources whose availability is heterogeneous in space and time. Much effort has been historically directed to studying migration as a response to seasonal, predictable fluctuations in resource availability in temperate species. A deeper understanding of how different migration patterns emerge in response to different patterns of resource variation requires describing migration patterns of species inhabiting less predictable environments, especially in tropical and subtropical areas. We provide the first individual‐based, quantitative description of migratory patterns in a subtropical wading bird in the southeastern United States, the wood stork (Mycteria americana). Using GPS tracking data for 64 individuals tracked between 2004 and 2017, we classified migratory behavior at the individual‐year level using information theory‐based model selection on nonlinear models of net squared displacement. We found that the wood stork population is partially migratory, with 59% of individuals seasonally commuting between winter ranges in Florida and summer ranges elsewhere in the population range (migrants), and 28% remaining in a single area in Florida year‐round (residents). Additionally, 13% of storks act as facultative migrants, migrating in some years but not in others. Comparing the distribution of residents and migrants suggests that different migratory strategies might be associated with the use of different or differently distributed resources, possibly including food supplementation from human activities. The existence of facultative migrants shows the potential for plastic change in migratory patterns. Partial migration in wood storks may be an adaptation to high heterogeneity and unpredictability of food resources. We suggest that future research should focus on wading birds as model species for the study of partial migration as an adaptation to heterogeneous and unpredictable environments.
We compare long-term movement behavior, breeding site philopatry, population dynamics and prey choice of White Ibises (Eudocimus albus) and Wood Storks (Mycteria americana) in order to illustrate (1) differences in strategies for exploiting spatially and temporally unpredictable food resources in wetlands of the southeastern U.S., and (2) the temporal and geographic scale at which conservation strategies for these species must be targeted. Since the 1930s, the U.S. White Ibis population has made a series of long-range (>400 km) shifts in the center of its breeding range. Very large colonies seem to exist for less than 15 years, and to be supported by at least 800 km2 of wetlands. Movements may be prompted either by degrading breeding conditions caused by both man-made and natural disturbances, or by attraction to abnormally high concentrations of prey. Wood Storks have also undergone large scale shifts in the center of breeding, but are much more philopatric to breeding sites (often >25 yr). They may be locally buffered from the unpredictability of food resources by the ability to forage at large distances from their colonies, and by being associated with more permanent wetlands. Preservation of specific colony sites and associated wetlands may well aid in conserving Wood Stork populations. In contrast, nomadic ibises require a different conservation approach, one that protects a geographically widespread network of wetland ecosystems.
Wood Storks (Mycteria americana) breeding in the southeastern United States exhibit lengthy inter- and intra-regional movements in response to resource availability. One type of movement, post-breeding dispersal, has resulted in storks from this population temporarily moving into the Gulf Coast states of Alabama and eastern Mississippi. Concurrently, other Wood Storks, presumably of Mexican/Central American origin, are frequently observed in large numbers in the Mississippi River Valley and nearby western states during the late-summer months and the proximity of dispersing storks from the two regions might result in population mixing. In a preliminary examination of the origins of Wood Storks observed in Gulf Coast states and the likelihood of population mixing, we deployed ten satellite transmitters on storks in those areas in June-July of 2003 and monitored their movements. All storks captured in eastern Mississippi moved into southern Florida. Storks captured in western Mississippi went to eastern Mexico or western Guatemala. One stork from Louisiana went to Mexico and the other went to southern Florida, suggesting that population mixing may be occurring on their non-breeding season habitats.
We used mitochondrial DNA (mtDNA) sequences to investigate the demographic history of the wood stork (Mycteria americana) populations in the Brazilian Pantanal. Sequences of 390/460 bp fragment of the mtDNA control region were analyzed in 62 wood stork specimens from 8 colonies using neutrality tests, phylogeographic, and coalescent analyses. Population expansion was supported by the significantly negative values of Tajima's (D = -2.071) and Fu's (Fs = -14.544) statistics and the unimodal pattern of mismatch distribution. Nested clade analyses indicated a historic range expansion event and recurrent gene flow that was restricted by isolation by distance as explanations for the haplotype distribution among the sampled colonies. High genetic diversity and the strictly unidirectional gene flow pattern emphasized the conservation importance of preserving the southern Pantanal colonies. Coalescence analy-ses suggested that northern and southern colonies diverged approximately 6,250 years before the present (YBP), and that their most recent common ancestor was approximately 18,900 YBP. Our results suggest that the contempo-rary wood stork Pantanal population originated from a more geographically limited founder population. Potential source populations may have occurred in the southern Pantanal or ancestry may reside in populations inhabiting the Brazilian central plateau or areas closer to the equatorial region.
The wood stork (Mycteria americana) is a colonial wading bird that inhabits the Neotropical region from the southeastern United States (US) to northern Argentina. The species is considered to be endangered in the US due to degradation of its foraging and breeding habitat. In other parts of its range, such as in the Brazilian Pantanal region, breeding populations of this species appear to be stable. We compared the levels of genetic variability and population structuring of the US and the Pantanal breeding populations using mitochondrial DNA (mtDNA) control region sequences. Twenty-seven haplotypes were identified among 88 wood stork samples collected from eight breeding colonies in the US and eight in the Pantanal. Patterns indicative of heteroplasmy were observed in 35.3% of the mtDNA sequences that were examined. Significantly higher levels of haplotype diversity were observed in the Pantanal samples compared to those from the US, suggesting that during the last century, demographic declines or a recent evolutionary bottleneck reduced the levels of mtDNA variability of the US population. Analyses of genetic structuring revealed non-significant genetic differentiation between these regions, indicating that either the populations were only recently separated or that gene flow continues to occur at low levels. Haplotype network analysis indicated low current levels of gene flow between populations that were closely related in the past.
The Wood Stork (Mycteria americana) is a colonial wading bird of the tropical and lower subtropical zones. We assessed genetic structure within and among five stork colonies from the Brazilian Pantanal and compared our data with those from North American populations. Samples of 234 individuals were studied using protein electrophoresis to evaluate genetic variability and interpopulation differentiation. Of 22 loci examined, 7 were polymorphic (mean heterozygosity = 0.068). The low Fst value (0.005) indicated little intraspecific variation among breeding colonies. Estimated number of migrants per generation based on private alleles (Nm = 11.3) and on Fst (48.8) suggests high gene flow Nei's genetic distance values among Pantanal colonies ranged from 0.0001 to 0.0034, demonstrating low genetic divergence among populations. Our data can be explained by supposing high gene flow levels among Pantanal colonies, and between North and South American populations, intermediated by a probable interbreeding population in Central America.
The breeding population of Wood Storks (Mycteria americana) in the southeastern United States has declined since the 1930s, resulting in the listing of all United States populations of the species as endangered in 1984. We assessed genetic structure within and among nine colonies of Wood Storks from Georgia and Florida. Levels of band sharing based on multilocus oligonucleotide DNA fingerprinting of individuals from seven colonies ranged from 58% among nests within the same tree to approximately 55% within the same colony. Levels of band sharing were similar to those reported for other populations of birds that have experienced drastic reductions in population size. A more thorough analysis of four polymorphic microsatellite loci for 136 individuals from nine colonies indicated low levels of allelic diversity and low genetic divergence among colonies. Genetic differentiation (P(ST) = 0.015) was similar to levels detected from allozymes for 15 colonies of Wood Storks in Florida:=(P(ST) = 0.019). These data, together with demographic studies of these populations, indicated high levels of gene flow among colonies (N(m) = 16.4). In agreement with previous studies, we recommend that all colonies of Wood Storks in the southeastern United States be managed on a regional basis as a single interbreeding population. Similar genetic surveys of the disjunct breeding populations of Wood Storks in South America and Central America would be beneficial in understanding the total genetic differentiation in the species.
Seasonal migration and the dispersal of juvenile and adult Wood Storks (Mycteria americana) after breeding have been documented in the United States, but little is known about the post-breeding movements of Wood Storks in South America. Our objective was to identify the locations of post-breeding areas used by Wood Storks banded as nestlings in breeding colonies in Brazil by analyzing banding data. During the period from 1984 to 2007, 2543 nestlings were banded at breeding colonies in three regions of Brazil, with most (94%) banded in the Pantanal wetland in west-central Brazil. Seventeen bands were subsequently recovered, with most (14) recovered in southern Brazil and northern Argentina. The mean distance between banding and recovery sites was 1265 km. Our results suggest that Wood Stork movements from breeding areas in Brazil are, as also reported in the United States, in response to changing water levels. The rainy season begins at the end of the breeding season and, in apparent response to rising water levels, Wood Storks in our study moved to drier areas further south with shallower water where they can forage more efficiently. Because only a small percentage of the area where Wood Stork bands were recovered in our study is currently protected, measures are needed to prevent habitat destruction and preserve wetland habitats used by Wood Storks during the post-breeding period in southern Brazil and Argentina.
The Wood Stork ( Mycteria americana ) is a wading bird inhabiting subtropical and tropical regions of the American continent. This species is considered endangered in the United States. We compared variability and genetic structuring of nine Brazilian Pantanal subpopulations with an North American population using eight allozyme loci data (MPI, ICD, NSP, EST‐D, LDH, PGM, 6PGD, and PEP‐A) and four microsatellite loci data (WS1, WS2, WS4, and WS6). Average expected heterozygosity of Pantanal population was similar (0.198 ± 0.065) to that expected for the North American population (0.231 ± 0.066). No significant genetic differentiation was found among Pantanal subpopulations ( F st = 0.012) and low differentiation was detected between Pantanal and North American populations (F st = 0.023). Lack of differentiation among Pantanal subpopulations may have been due to high gene flow level among birds of neighbor breeding colonies and low natal philopatry. We propose that low differentiation between North and South American populations has arisen either because these populations occupied neighboring regions during late glaciation or because there is a continuous gene flow between them, via Central American or northern South American populations.
RESUMO
O Cabeça‐seca ( Mycteria americana ) é uma ave aquática habitante das regiões tropicais e subtropicais do continente americano. Essa espécie está ameaçada de extinção nos Estados Unidos. Nós comparamos a variabilidade e a estruturação genética de nove subpopulações brasileiras do Pantanal com as da população norte americana, baseando‐se em dados de oito locos alozímicos (MPI, ICD, NSP, EST‐D, LDH, PGM, 6PGD, e PEP‐A) e em dados de quatro locos de microssatélites (WS1, WS2, WS4, e WS6). A heterozigosidade média esperada para a população do Pantanal (0.198 ± 0.065) foi semelhante á esperada para a população norte americana (0.231 ± 0.066). Não foi encontrada diferenciação genética significativa entre as subpopulaçóes do Pantanal ( F st = 0.012) e baixa diferenciação genética foi detectada entre as populações do Pantanal e a norte americana (. F st = 0.023). A não diferenciação entre subpopulações do Pantanal pode ser resultante de um alto nível do fluxo génico entre aves de colónias reprodutivas vizinhas e da baixa filopatria natal. Nós propomos que a baixa diferenciação entre as populações norte e sul americanas seja decorrente da ocupaçaTo de regiões vizinhas por essas populações durante a última glaciação ou devido á existéncia de fluxo contínue entre elas, via populações da América Central ou do norte da América do Sul.
Metapopulation biology is concerned with the dynamic consequences of
migration among local populations and the conditions of regional
persistence of species with unstable local populations. Well established
effects of habitat patch area and isolation on migration, colonization
and population extinction have now become integrated with classic
metapopulation dynamics. This has led to models that can be used to
predict the movement patterns of individuals, the dynamics of species,
and the distributional patterns in multispecies communities in real
fragmented landscapes.
The general conclusion of part I is that the theoretical correlation between representatives of a locus in gametes, uniting or otherwise, relative to one or another array of such representatives (F-statistics), gives a broader basis for comparison of population structures, including progress in fixation, than does the alternative concept: the probability of identity of such representatives by origin. One reason is that correlations vary from -1 to +1 while probabilities vary only from 0 to +1. The probability concept gives, however, a very useful supplementary interpretation where applicable. The relation of the basic set of F-statistics, FIT, FIS, FST, to variances within populations is discussed in part II and applications to diverse patterns of population structure are reviewed (the island model with or without selective differences, isolation by distance in continuous populations under balancing of local inbreeding and dispersion, uniformly distributed clusters under a similar balance, selective clines, breeds of livestock). In part III, these F-statistics are applied to systems of mating in populations of given small size, in which consanguine mating is either avoided as much as possible, or pursued as much as is possible without any disruption of the group. The apparently paradoxical result obtained by Kimura and Crow that heterozygosis declines more rapidly under the former than under the latter is discussed from the standpoint of these statistics. These systems have been found to agree in one respect, the ultimate proportion of recombinant lines in the race between fixation and recombination among lines starting from double heterozygotes.
In the face of continuing habitat fragmentation and isolation, the optimal level of connectivity between populations has become a central issue in conservation biology. A common rule of thumb holds that one migrant per generation into a subpopulation is sufficient to minimize the loss of polymorphism and heterozygosity within subpopulations while allowing for divergence in allele frequencies among subpopulations. The one-migrant-per-generation rule is based on numerous simplifying assumptions that may not hold in natural populations. We examine the conceptual and theoretical basis of the rule and consider both genetic and nongenetic factors that influence the desired level of connectivity among subpopulations. We conclude that one migrant per generation is a desirable minimum, but it may be inadequate for many natural populations. We suggest that a minimum of 1 and a maximum of 10 migrants per generation would be an appropriate general rule of thumb for genetic purposes, bearing in mind that factors other than genetics may further influence the ideal level of connectivity.
International Union for the Conservation of Nature (IUCN). 2016. Mycteria americana: BirdLife International: The IUCN red list of threatened species 2016:e. T22697648A93627312. International Union for Conservation of Nature
- R A Hylton
Hylton, R.A. 2004. Survival, movement patterns, and habitat use of juvenile Wood Storks,
Mycteria americana. University of Florida. Available online at http://purl.fcla.edu/fcla/
etd/UFE0007007. Accessed 11 October 2017.
International Union for the Conservation of Nature (IUCN). 2016. Mycteria americana: BirdLife International: The IUCN red list of threatened species 2016:e.
T22697648A93627312. International Union for Conservation of Nature. Available online at http://www.iucnredlist.org/details/22697648/0. Accessed 12 October 2017.
Satellite tracking of Wood Storks (Mycteria americana) in the southeastern United States
- A Savage
- E F Stevens
- F W Koontz
- C Koontz
- L Brisbin
- A L Bryan
- J Robinette
Savage, A., E.F. Stevens, F.W. Koontz, C. Koontz, L. Brisbin, A.L. Bryan Jr., and J. Robinette. 1999. Satellite tracking of Wood Storks (Mycteria americana) in the southeastern
United States. Endangered Species Update 16:64-66.
Genetic variation and population structure of the Florida Wood Stork
- P W Stangel
- J A Rodgers
- A L Bryan
Stangel, P.W., J.A. Rodgers, and A.L. Bryan. 1990. Genetic variation and population structure of the Florida Wood Stork. The Auk 107:614-619.
Endangered and threatened wildlife and plants; reclassification of the US breeding population of the Wood Stork from Endangered to Threatened
- Wildlife Us Fish
- Service
US Fish and Wildlife Service (USFWS). 2014. Endangered and threatened wildlife and
plants; reclassification of the US breeding population of the Wood Stork from Endangered to Threatened. Federal Register, Washington, DC, USA.