dispersal distances
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2021 ◽  
Author(s):  
Katharine F.E. Hogan ◽  
Dillon T. Fogarty ◽  
Hugh Ellerman ◽  
Christopher T. Fill ◽  
Daniel Morales ◽  
...  

Abstract Roadsides can be vectors for tree invasion within grasslands by bisecting landscapes and facilitating propagule spread to interior habitat. Current invasive tree management in North America’s Great Plains focuses on reducing on-site (i.e., interior habitat) vulnerability through on-site prevention and eradication, but invasive tree management of surrounding areas known to serve as invasion vectors, such as roadsides and public rights-of-ways, is sporadic. We surveyed roadsides for invasive tree propagule sources in a southeastern Nebraska grassland landscape to determine how much of the surrounding landscape is potentially vulnerable to roadside invasion, and by which species, and thereby, provide insights into the locations and forms of future landcover change. Invasive tree species were widespread in roadsides. Given modest seed dispersal distances of 100-200 m, our results show that roadsides have potential to serve as major sources of grassland exposure to tree invasion, compromising up to 44% of grasslands in the Denton Hills. Under these dispersal distances, funds spent removing trees on grassland properties may have little impact on the landscape’s overall vulnerability, due to exposure driven by roadside propagule sources. A key implication from this study is that roadsides, while often neglected from management, represent an important component of integrated management strategies for reducing grassland vulnerability to tree invasion.


2021 ◽  
Vol 9 ◽  
Author(s):  
John R. Poulsen ◽  
Christopher Beirne ◽  
Colin Rundel ◽  
Melissa Baldino ◽  
Seokmin Kim ◽  
...  

By dispersing seeds long distances, large, fruit-eating animals influence plant population spread and community dynamics. After fruit consumption, animal gut passage time and movement determine seed dispersal patterns and distances. These, in turn, are influenced by extrinsic, environmental variables and intrinsic, individual-level variables. We simulated seed dispersal by forest elephants (Loxodonta cyclotis) by integrating gut passage data from wild elephants with movement data from 96 individuals. On average, elephants dispersed seeds 5.3 km, with 89% of seeds dispersed farther than 1 km. The longest simulated seed dispersal distance was 101 km, with an average maximum dispersal distance of 40.1 km. Seed dispersal distances varied among national parks, perhaps due to unmeasured environmental differences such as habitat heterogeneity and configuration, but not with human disturbance or habitat openness. On average, male elephants dispersed seeds farther than females. Elephant behavioral traits strongly influenced dispersal distances, with bold, exploratory elephants dispersing seeds 1.1 km farther than shy, idler elephants. Protection of forest elephants, particularly males and highly mobile, exploratory individuals, is critical to maintaining long distance seed dispersal services that shape plant communities and tropical forest habitat.


2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Rose J. Swift ◽  
Michael J. Anteau ◽  
Kristen S. Ellis ◽  
Megan M. Ring ◽  
Mark H. Sherfy ◽  
...  

Abstract Background Dispersal is a critical life history strategy that has important conservation implications, particularly for at-risk species with active recovery efforts and migratory species. Both natal and breeding dispersal are driven by numerous selection pressures, including conspecific competition, individual characteristics, reproductive success, and spatiotemporal variation in habitat. Most studies focus on dispersal probabilities, but the distance traveled can affect survival, fitness, and even metapopulation dynamics. Methods We examined sources of variation in dispersal distances with 275 natal dispersal and 1335 interannual breeding events for piping plovers (Charadrius melodus) breeding in the Northern Great Plains between 2014 and 2019. Results Natal dispersal was on average longer (mean: 81.0 km, median: 53 km) than adult breeding movements (mean: 23.7 km, median: 1 km). Individuals moved the shortest distances when hatched, previously nested, or settling on river habitats. When more habitat was available on their natal area than in the year prior, hatch-year birds moved shorter distances to their first breeding location. Similarly, adults also moved shorter distances when more habitat was available at the settling site and when in closer proximity to other known nesting areas. Additionally, adult movement distance was shorter when successfully hatching a nest the year prior, retaining a mate, or initiating a current nest earlier. Conclusion Habitat availability appears to be associated with dispersal distance for both hatch-year and adult piping plovers. Conservation efforts that integrate dispersal distances may benefit from maintaining nesting habitat within close proximity to other areas for adults and a network of clustered sites spread out across a larger landscape for natal dispersal.


2021 ◽  
Author(s):  
◽  
Hilary Misha Cresko

<p>Sex ratio imbalances in wild bird populations have been a challenge for wildlife managers for decades. Differences between sexes during natal dispersal has long been thought to promote sex ratio imbalances. Natal dispersal distances may differ between sexes because of competition for food and space, or intrasexual competition and aggression. I investigated natal dispersal and intrasexual competition as mechanisms for a sex ratio imbalance in a small, translocated population of a New Zealand honeyeater, the bellbird (Anthornis melanura) in the Karori Wildlife Sanctuary- Zealandia, Wellington, New Zealand. I analysed long term records of population size and structure to document annual variation in sex ratios since the reintroduction of bellbirds to Zealandia. Radio telemetry was used to track the 2008/2009 cohort of bellbirds for five months after fledging to observe movements and distances travelled from their hatching location. Observations at a supplemental food source that was used by both adults and fledglings, were used to study intrasexual competition and aggression. Dispersal distances did not differ between the sexes for any of the measurement types used. Males did however significantly dominate the use of a supplemental food source and were significantly more aggressive around this food source, which is most likely responsible for the lower feeding rate among females. Therefore, I conclude that the sex ratio imbalance in the bellbird population in Zealandia may not result from a difference in natal dispersal, but from males dominating a supplemental food source, raising their population and fitness over that of females.</p>


2021 ◽  
Author(s):  
◽  
Hilary Misha Cresko

<p>Sex ratio imbalances in wild bird populations have been a challenge for wildlife managers for decades. Differences between sexes during natal dispersal has long been thought to promote sex ratio imbalances. Natal dispersal distances may differ between sexes because of competition for food and space, or intrasexual competition and aggression. I investigated natal dispersal and intrasexual competition as mechanisms for a sex ratio imbalance in a small, translocated population of a New Zealand honeyeater, the bellbird (Anthornis melanura) in the Karori Wildlife Sanctuary- Zealandia, Wellington, New Zealand. I analysed long term records of population size and structure to document annual variation in sex ratios since the reintroduction of bellbirds to Zealandia. Radio telemetry was used to track the 2008/2009 cohort of bellbirds for five months after fledging to observe movements and distances travelled from their hatching location. Observations at a supplemental food source that was used by both adults and fledglings, were used to study intrasexual competition and aggression. Dispersal distances did not differ between the sexes for any of the measurement types used. Males did however significantly dominate the use of a supplemental food source and were significantly more aggressive around this food source, which is most likely responsible for the lower feeding rate among females. Therefore, I conclude that the sex ratio imbalance in the bellbird population in Zealandia may not result from a difference in natal dispersal, but from males dominating a supplemental food source, raising their population and fitness over that of females.</p>


Western Birds ◽  
2021 ◽  
Vol 52 (4) ◽  
pp. 296-310
Author(s):  
Carolyn A. Cook ◽  
Glen T. Hvenegaard ◽  
Geoffrey L. Holroyd ◽  
Hardy Pletz ◽  
Myrna Pearman

Dispersal patterns deepen our understanding of population dynamics. Dispersal by all age and sex classes enhances a species’ ability to respond to environmental changes, such as in habitat availability, artificial nest sites, and climate. The migration dynamics of the eastern subspecies of the Purple Martin (Progne subis subis) are well known, but we know less about its patterns of annual dispersal. We compared the frequency, distance, and direction of dispersal by each age/sex cohort of martins in central Alberta, at the northwestern limit of their breeding range. We used two datasets: (1) adult martins banded in central Alberta as nestlings and encountered during the summers of 2017 and 2018, and (2) records of encounters of banded martins in Canada from 1935 to 2016 from the Canadian Wildlife Service’s Bird Banding Office. In Alberta, 36% of birds dispersed from natal sites (by an average distance of 24 km), most commonly to the northeast. Across Canada, 29% of birds dispersed (by an average distance of 183 km), most commonly to the east and northeast. In Alberta, martins at least two years old dispersed less frequently than yearlings since some older martins returned to their natal site after first breeding elsewhere. Dispersal distances of after-second-year martins, which represent natal plus breeding dispersal, were greater than those of second-year birds, which represent natal dispersal alone. Thus some martins continue to disperse after their second year and do not maintain complete fidelity to a breeding site, which is different from our current understanding.


Author(s):  
Barney P. Caton ◽  
Hui Fang ◽  
Nicholas C. Manoukis ◽  
Godshen R. Pallipparambil

2021 ◽  
Author(s):  
Fiona Joanne Thomson

Abstract Understanding dispersal and establishment patterns of invasive plant species is critical information to help control and eradicate their populations. Euphorbia paralias, sea spurge, is a highly invasive weed that can be a serious threat to coastal environments. Two recent incursions of E. paralias on New Zealand’s coastline consisted of one reproductive adult surrounded by several hundred juveniles, providing the opportunity to gather effective dispersal distance data for this species. Using these two separate populations effective dispersal distances curves were created for E. paralias. It was found one adult led to the establishment of 213 healthy plants at NZ’s southern-most incursion and 484 healthy plants at the northern-most incursion. All plants were subsequently removed from the site. The maximum effective dispersal distance of 15.8m on land for E. paralias was larger than would be predicted by the majority of trait-based dispersal distance models and the estimate of ~ 2m in the literature. These results show that E. paralias can establish large healthy populations, making it a considerable threat to coastal environments. However, populations around an adult plant are fairly concentrated at the very early stages of invasion (90% of offspring < 5.5m from the adult) providing opportunities to remove the seed bank at incursion sites. Early detection of E. paralias populations using comprehensive surveillance and removal of any new populations (seed and establishing plants) will be essential components for the success in any eradication programme for sea spurge.


PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0256038
Author(s):  
Bettina Almasi ◽  
Carolina Massa ◽  
Lukas Jenni ◽  
Alexandre Roulin

Natal dispersal affects many processes such as population dynamics. So far, most studies have examined the intrinsic and extrinsic factors that determine the distance between the place of birth and of first breeding. In contrast, few researchers followed the first steps of dispersal soon after fledging. To study this gap, we radio-tracked 95 barn owl nestlings (Tyto alba) to locate their diurnal roost sites from the fledging stage until December. This was used to test whether the age of nest departure, post-fledging movements and dispersal distance were related to melanin-based coloration, which is correlated to fitness-related traits, as well as to corticosterone, a hormone that mediates a number of life history trade-offs and the physiological and behavioural responses to stressful situations. We found that the artificial administration of corticosterone delayed the age when juveniles left their parental home-range in females but not in males. During the first few months after fledging, longer dispersal distances were reached by females compared to males, by individuals marked with larger black feather spots compared to individuals with smaller spots, by larger individuals and by those experimentally treated with corticosterone. We conclude that the onset and magnitude of dispersal is sensitive to the stress hormone corticosterone, melanin-based coloration and body size.


2021 ◽  
Vol 17 (8) ◽  
pp. e1009315
Author(s):  
David R. J. Pleydell ◽  
Samuel Soubeyrand ◽  
Sylvie Dallot ◽  
Gérard Labonne ◽  
Joël Chadœuf ◽  
...  

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