As a postdoctoral researcher at Max Planck Institute for Ornithology, I am studying a complex relationship among
site fidelity, mating system, and migration strategy in migratory shorebirds that breed in the Arctic.
Within a relatively short time since the last glacial maximum, shorebirds have evolved a diverse range of mating systems, in complex association with sexual size dimorphism, ontogenetic growth rate, parental care and migration strategies. Although diverse, shorebird reproductive strategies are frequently divided into ‘conservative’ and ‘opportunistic’ modes of adapting to the Arctic environment. ‘Conservative breeders’ are often faithful to specific breeding locations and their previous mates, breed early in the season, and provide biparental care to offspring. On the other hand, ‘opportunistic breeders’, ranging from sequential polygamy to being promiscuous, are less faithful to breeding locations, tend to breed later in the season, and provide uniparental care.
Among the 37 species of Scolopacidae shorebirds breeding in North America, there are two species, whose life-history strategy does not fit either strategy:
long-billed dowitcher (Limnodromus scolopaceus) and Baird’s sandpiper (Calidris bairdii).
My research questions are
site fidelity, mating system, and migration strategy in migratory shorebirds that breed in the Arctic.
Within a relatively short time since the last glacial maximum, shorebirds have evolved a diverse range of mating systems, in complex association with sexual size dimorphism, ontogenetic growth rate, parental care and migration strategies. Although diverse, shorebird reproductive strategies are frequently divided into ‘conservative’ and ‘opportunistic’ modes of adapting to the Arctic environment. ‘Conservative breeders’ are often faithful to specific breeding locations and their previous mates, breed early in the season, and provide biparental care to offspring. On the other hand, ‘opportunistic breeders’, ranging from sequential polygamy to being promiscuous, are less faithful to breeding locations, tend to breed later in the season, and provide uniparental care.
Among the 37 species of Scolopacidae shorebirds breeding in North America, there are two species, whose life-history strategy does not fit either strategy:
long-billed dowitcher (Limnodromus scolopaceus) and Baird’s sandpiper (Calidris bairdii).
My research questions are
- how this relatively rare intermediate strategy maintain monogamy with no site fidelity?
- Why are they monogamous when their settlement strategy is seemingly opportunistic?
- And, does the opportunistic settlement strategy promote flexible search for a better breeding condition?
Reproductive settlement strategies of conservative breeders, opportunistic breeders, and the long-billed dowitcher described as arrows in the time-space plain. Top: Each shaded bar represents a potential breeding window (y-axis) with a varying environmental condition at a given breeding location (x-axis) for any given year. Conservative breeders may occupy the same space (site A) and adjust their timing of breeding to the optimal breeding condition on that site and year. This high site fidelity is often coupled with high mate fidelity. Opportunistic breeders may show a nomadic movement across the time-space plain and occupy any space within their breeding range for a given year. Bottom: As a result, the inter-annual variability in the timing and location of breeding within individual is relatively small for conservative breeders and bigger for opportunistic breeders. Correspondingly, when unexpected environmental changes occur, the opportunistic strategy may allow faster, adaptable response via modifying both the timing and location of breeding. Long-billed dowitcher is a puzzling species and shows an intermediate strategy where an opportunistic settlement pattern is coupled with monogamy. However, the available information on the species’ breeding and migration strategies are based on sparse data.
As a postdoctoral researcher at Virginia Tech, I examined long-term population drivers of shorebirds on the Atlantic coast.
Identifying the drivers of long-term population change is complicated by a number of extrinsic factors that often covary with time and by intrinsic factors that operate on a time lag. For migratory shorebirds that breed on the barrier islands of eastern North America, populations may be limited by the anthropogenic, climatic, biological, or physical environments they encounter throughout the annual cycle.
Using three-decades (1985–2017) of population monitoring data collected by the National Park Service at two national seashores in North Carolina,
I examined the potential drivers of Piping Plover (Charadrius melodus) and American Oystercatcher (Haematopus palliates) populations nesting there. Our modelling revealed a strong effect of human activity and subsequent protection efforts to reduce disturbance on the population trajectory of plovers, but only a weak effect of breeding and wintering climatic conditions, population productivity, and nesting habitat availability.
Management and conservation plans for migratory species require abundance estimates that are near the true population size though they are difficult to obtain. Thus, in a separate project, I applied a set of generalized N‐mixture models to simulated count data to test their applicability for transient populations. With knowledge from the simulated data, I then applied these models to daily counts of staging migratory shorebirds and estimated daily abundances accounting for variation in the detection and immigration rates. This study provided the first empirical application of the generalized N‐mixture model that incorporates temporal trends in immigration and estimates daily abundance of a staging unmarked migratory population.
Using three-decades (1985–2017) of population monitoring data collected by the National Park Service at two national seashores in North Carolina,
I examined the potential drivers of Piping Plover (Charadrius melodus) and American Oystercatcher (Haematopus palliates) populations nesting there. Our modelling revealed a strong effect of human activity and subsequent protection efforts to reduce disturbance on the population trajectory of plovers, but only a weak effect of breeding and wintering climatic conditions, population productivity, and nesting habitat availability.
Management and conservation plans for migratory species require abundance estimates that are near the true population size though they are difficult to obtain. Thus, in a separate project, I applied a set of generalized N‐mixture models to simulated count data to test their applicability for transient populations. With knowledge from the simulated data, I then applied these models to daily counts of staging migratory shorebirds and estimated daily abundances accounting for variation in the detection and immigration rates. This study provided the first empirical application of the generalized N‐mixture model that incorporates temporal trends in immigration and estimates daily abundance of a staging unmarked migratory population.
For my PhD research at Kansas State University, I studied breeding ecology of Arctic shorebirds in relation to climate change.
In 2010, Dr. Brett K. Sandercock at Kansas State University gave me an amazing opportunity to go to Alaska and study arctic-breeding shorebirds.
For the following 5.5 years, I investigated patterns of climate change at a network of Arctic sites in Alaska and Canada,
and examined the impacts of climate change on the breeding phenology, reproductive performance, and trophic interactions of
arctic-breeding shorebirds.
Comparing the breeding performance of three sympatric shorebird species, western sandpiper, semipalmated sandpiper, and red-necked phalarope, at Nome, Alaska across a 14-year interval, I found that shorebirds responded to a cooling climate by delaying timing of breeding. Delayed breeding shortened the incubation duration for two biparental species but extended incubation for a uniparental species. Despite a short Arctic summer, the breeding windows of three sympatric species were temporally distinct. The three species often nested within several meters from each other, but bred under different temperature and precipitation regimes and adjusted their reproductive output to different sets of environmental factors.
Shifts in breeding phenology can disrupt trophic interactions, especially the phenological match between peak prey availability and hatching of shorebirds.
Comparing the extent of phenological mismatch between six arctic-breeding shorebirds and their invertebrate prey at ten Arctic sites, I found great variation in the degree of phenological mismatch between the two trophic levels. Latitudinal and longitudinal gradients in the extent of trophic mismatch were mediated through geographic variation in seasonal phenology of invertebrates and shorebirds.
For the following 5.5 years, I investigated patterns of climate change at a network of Arctic sites in Alaska and Canada,
and examined the impacts of climate change on the breeding phenology, reproductive performance, and trophic interactions of
arctic-breeding shorebirds.
Comparing the breeding performance of three sympatric shorebird species, western sandpiper, semipalmated sandpiper, and red-necked phalarope, at Nome, Alaska across a 14-year interval, I found that shorebirds responded to a cooling climate by delaying timing of breeding. Delayed breeding shortened the incubation duration for two biparental species but extended incubation for a uniparental species. Despite a short Arctic summer, the breeding windows of three sympatric species were temporally distinct. The three species often nested within several meters from each other, but bred under different temperature and precipitation regimes and adjusted their reproductive output to different sets of environmental factors.
Shifts in breeding phenology can disrupt trophic interactions, especially the phenological match between peak prey availability and hatching of shorebirds.
Comparing the extent of phenological mismatch between six arctic-breeding shorebirds and their invertebrate prey at ten Arctic sites, I found great variation in the degree of phenological mismatch between the two trophic levels. Latitudinal and longitudinal gradients in the extent of trophic mismatch were mediated through geographic variation in seasonal phenology of invertebrates and shorebirds.
For a Master's research in South Korea, I studied the wind-adaptive nest structure of black-billed magpies.
Black-billed magpies in South Korea build their nests in tall trees where strong wind can reduce structural stability and microclimate of the nests.
To circumvent the problem, magpies can build streamlined nests so that the direction of the longest horizontal axis matches that of the strongest or the most prevalent wind.
I measured the morphological characteristics of 89 magpies nests in four sites with different wind conditions.
At all four sites, nests were streamlined and oriented toward the direction of the strongest wind. Nest wall was thicker and more densely woven at sites with faster wind speed.
Body condition index of nestlings measured at one study site was positively correlated with the degree of streamlinedness of the nest and the amount of fabric material used to line the nest cup.
Potential benefits of streamlined shape were investigated though a computational modeling approach. Two-dimensional models of magpie nests showed that, as the length of the longest horizontal axis increased, the maximum disparity between wind pressure at both tips of nests decreased. Three-dimensional models also showed that the streamlined-shape and thicker nest wall greatly reduced the degree of wind transmission.
Field observation and computational simulation suggest that black-billed magpies optimize the structure and orientation of their nests in order to minimize the wind-induced risk and gain the structural stability and control over microclimate in the nest.
To circumvent the problem, magpies can build streamlined nests so that the direction of the longest horizontal axis matches that of the strongest or the most prevalent wind.
I measured the morphological characteristics of 89 magpies nests in four sites with different wind conditions.
At all four sites, nests were streamlined and oriented toward the direction of the strongest wind. Nest wall was thicker and more densely woven at sites with faster wind speed.
Body condition index of nestlings measured at one study site was positively correlated with the degree of streamlinedness of the nest and the amount of fabric material used to line the nest cup.
Potential benefits of streamlined shape were investigated though a computational modeling approach. Two-dimensional models of magpie nests showed that, as the length of the longest horizontal axis increased, the maximum disparity between wind pressure at both tips of nests decreased. Three-dimensional models also showed that the streamlined-shape and thicker nest wall greatly reduced the degree of wind transmission.
Field observation and computational simulation suggest that black-billed magpies optimize the structure and orientation of their nests in order to minimize the wind-induced risk and gain the structural stability and control over microclimate in the nest.