Hots dogs, chicken wings and city living helped wetland wood storks
thrive
Study of wetland birds finds city storks fared better than their non-
urban counterparts in suboptimal natural conditions

Date:
August 31, 2020
Source:
Florida Atlantic University
Summary:
Using the Wood Stork, researchers compared city storks with natural
wetland storks to gauge their success in urban environments based on
their diet and food opportunities. Results provide evidence of how
a wetland species persists and even thrives in an urban environment
by switching to human foods like chicken wings and hots dogs when
natural marshes are in bad shape. These findings indicate that
urban areas can buffer a species from the unpredictability of
natural food sources.



FULL STORY ========================================================================== Natural wetlands continue to disappear due to city and human development
and are being replaced with humanmade swales, ponds and canals. This degradation and replacement of natural wetlands suggest that urban areas
may be imperative to wetland species, especially when natural conditions
are unpredictable.

Wetland birds are often seen in and around cities; however, they have
been largely ignored in urban wildlife studies. In their historic ranges, wetland birds inhabit dynamic marshes, traveling long distances to locate
food. Yet, does their ability to forage for food in natural environments translate to their ability to do so in an urban environment?

========================================================================== Using the Wood Stork (Mycteria americana), a large American wading bird
found throughout southeastern swamps and wetlands, scientists from
Florida Atlantic University's Charles E. Schmidt College of Science
compared city storks with natural wetland storks to gauge their success
in urban environments based on their diet and food opportunities.

Results of the study, published in Scientific Reports, provide evidence
and a systematic understanding of how a wetland species persists and
even thrives in an urban environment, by switching to human foods like
chicken wings and hot dogs when natural marshes are in bad shape.

For the study, researchers sampled 160 nests during the 2015-2017 nesting seasons. Of the 160 sampled nests, 106 nests were in three urban colonies
and 54 nests were in two natural wetland colonies in South Florida where a
vast freshwater wetland, the Everglades, is located adjacent to a large
urban area.

They compared urban and natural wetland storks' productivity, body
condition, reproductive performance, breadth of diet, and tested whether
stork diets changed during suboptimal natural wetland conditions.

They found that storks were able to exploit urban areas when natural
food resources were scarce. This ability to switch between habitats
and thus resources allowed for better reproductive performance during
periods of low natural food availability. Furthermore, body condition
did not differ significantly between urban and natural wetland nesting
birds during either optimal or suboptimal conditions, suggesting that supplemental environmental resources do not negatively impact body
condition. These findings indicate that urban areas can buffer a species
from the unpredictability of natural food resources.

"During suboptimal conditions, urban birds expanded their diets to
include more prey types, including anthropogenic food, suggesting that
urban birds were able to exploit urban areas during low natural wetland
prey availability," said Betsy A. Evans, Ph.D., a natural resources
specialist with the United States Army Corps of Engineers and lead author,
who conducted the study as a graduate student in FAU's Department of
Biological Sciences with co-author Dale E.

Gawlik, Ph.D., a professor in biology and FAU's Environmental Science
Program.

"The ability of urban birds to switch their diet to include different
prey types such as human-provided food that included chicken wings and
hot dogs likely allowed them to produce more chicks during poor natural
wetland prey availability conditions than their non-urban counterparts."
Evans and Gawlik discovered that not only were urban storks able to
access human-provided food such as trash, but they also increased
the proportion of amphibians such as frogs in their diet when natural
wetland conditions were suboptimal. Larval frogs (tadpoles) occur in
a wide range of wetland types in the study region; however, they were
10 times more abundant in roadside created wetlands such as swales,
ponds and canals than in natural wetlands during the time-period of this
study. This suggests that storks may also have been accessing created
wetlands along roadways during suboptimal natural wetland conditions.

"Behavioral flexibility and the ability to travel long distances
and exploit resources in dynamic systems may give wetland birds an
ecological advantage in urban environments," said Gawlik. "Our findings demonstrated that urban storks expanded their diets during times of
low natural wetland prey availability to include resources commonly
found in urban areas, partially dampening the natural wetland food
limitation on wading bird populations. Natural wetland birds, however,
paid a greater reproductive penalty during suboptimal conditions than
their urban counterparts. Furthermore, this ability to switch diets
between resource pulses may reduce population fluctuations and lower the
risk of extinction." The study demonstrates that urban environments may support biodiversity in a variety of ways. To mitigate potential threats
from urbanization it will be important to understand how species exploit
new resources as well as how they are affected by loss of resources from
human activities.

For the study, the researchers visited two natural wetland colonies
and three urban colonies one to two times per week during the 2015-2017 breeding seasons (approximately March through June). They selected these
study colonies based on their range of hydrological conditions and history
of repeated use by nesting storks. They describe colony landscape type
broadly as either "urban" or "natural wetland" with natural wetland
colonies occurring within Everglades National Park and urban colonies
occurring within the urban east coast corridor of South Florida. At each
colony location, they marked individual nests from which they collected productivity, body condition, and diet information.

This research was partially supported by the Florida Department of Transportation (BDV27-922-02).


========================================================================== Story Source: Materials provided by Florida_Atlantic_University. Original written by Gisele Galoustian. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Betsy A. Evans, Dale E. Gawlik. Urban food subsidies reduce
natural food
limitations and reproductive costs for a wetland bird. Scientific
Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-70934-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200831094725.htm

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