GLMM with a binary distribution function, and controlling for saltpan area
(Crawley 2013). The saltpan identity was specified as a random factor.
Evaluating Effects on Wintering Shorebirds
As in the breeding season, wintering shorebirds can avoid potential impacts by
moving away from impacted saltpans (Cayford 1993). If they stay, they may
change their spatial distribution on impacted saltpans and their activity patterns,
which may eventually affect their winter survival, mainly by affecting energy intake
(Yasué et al. 2008; Robinson and Pollitt 2002). We monitored the number of all
wintering shorebirds, and assessed their distribution and patterns of activity
(Fig. 12.2), thereby testing the following hypothesis:
1. Shorebird abundance should decline in impacted saltpans in comparison to
control saltpans.
2. The distribution of shorebirds within impacted saltpans should change after the
beginning of the construction and operation of the railway.
3. The distribution and activity of shorebirds within impacted saltpans should
change after the beginning of the construction and operation of the railway.
Wintering Shorebird Abundance
We estimated the number of individuals of all shorebird species in the saltpans,
from counts carried out at regular intervals during the months of January and/or
February (3–5 sampling occasions). Given the small number of counts per species
and the associated overdispersion, we pooled the counts of all species. We tested for
differences in the total number of shorebirds with time of year and type of saltpan
(impacted vs. control), using a GLMM with a negative binomial distribution,
controlling for overdispersion and using the saltpan area as an offset (Crawley
2013). Saltpan identity and survey week were specified as random variables.
Shorebird Spatial Distribution and Activity Within Saltpans
Using the same rationale established for the breeding season, we recorded the
spatial distribution of shorebirds in each saltpan according to the type of pond
(feeders, evaporators, and crystallizers). We then tested for variation in the total
number of shorebirds in relation to the type of pond, time (year) and type of saltpan
(impacted vs control) using a GLMM with a negative binomial distribution, controlling for over-dispersion and saltpan area (Crawley 2013). Saltpan identity and
the survey week were specified as random variables.
We also recorded the activity (foraging vs roosting) of each shorebird. Because
activity budgets differ between species, we used only for Dunlin data for this
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T. Múrias et al.
(Crawley 2013). The saltpan identity was specified as a random factor.
Evaluating Effects on Wintering Shorebirds
As in the breeding season, wintering shorebirds can avoid potential impacts by
moving away from impacted saltpans (Cayford 1993). If they stay, they may
change their spatial distribution on impacted saltpans and their activity patterns,
which may eventually affect their winter survival, mainly by affecting energy intake
(Yasué et al. 2008; Robinson and Pollitt 2002). We monitored the number of all
wintering shorebirds, and assessed their distribution and patterns of activity
(Fig. 12.2), thereby testing the following hypothesis:
1. Shorebird abundance should decline in impacted saltpans in comparison to
control saltpans.
2. The distribution of shorebirds within impacted saltpans should change after the
beginning of the construction and operation of the railway.
3. The distribution and activity of shorebirds within impacted saltpans should
change after the beginning of the construction and operation of the railway.
Wintering Shorebird Abundance
We estimated the number of individuals of all shorebird species in the saltpans,
from counts carried out at regular intervals during the months of January and/or
February (3–5 sampling occasions). Given the small number of counts per species
and the associated overdispersion, we pooled the counts of all species. We tested for
differences in the total number of shorebirds with time of year and type of saltpan
(impacted vs. control), using a GLMM with a negative binomial distribution,
controlling for overdispersion and using the saltpan area as an offset (Crawley
2013). Saltpan identity and survey week were specified as random variables.
Shorebird Spatial Distribution and Activity Within Saltpans
Using the same rationale established for the breeding season, we recorded the
spatial distribution of shorebirds in each saltpan according to the type of pond
(feeders, evaporators, and crystallizers). We then tested for variation in the total
number of shorebirds in relation to the type of pond, time (year) and type of saltpan
(impacted vs control) using a GLMM with a negative binomial distribution, controlling for over-dispersion and saltpan area (Crawley 2013). Saltpan identity and
the survey week were specified as random variables.
We also recorded the activity (foraging vs roosting) of each shorebird. Because
activity budgets differ between species, we used only for Dunlin data for this
204
T. Múrias et al.