analysis, because this was the most abundant species. We tested for differences in
activity with time (year) and type of saltpan (impacted and control) using a GLMM
with a binomial distribution function, controlling for saltpan area (Crawley 2013).
Results
Effects on Breeding Shorebirds
Shorebird Abundances
The average abundance of breeding shorebirds presented large variations, which
ranged from the complete absence in some saltpans, in a breeding season, to
maximum average values per saltpan of 36.2 Black-winged stilts (9.3 birds/ha),
26.0 Kentish plovers (7.9 birds/ha) and 89.7 Little terns (23.0 birds/ha) in 2006. For
the three focal species, there was a significant interaction term between time and
type of pond (Table 12.1), thus pointing out an impact of the construction and
operation of the railway viaduct. Regarding the construction phase, there were
significant increases in the abundance of Kentish plover (2008) and Little tern
(2008 and 2009) in impacted saltpans in relation to the expectation from temporal
trends at control saltpans (Table 12.1). However, during the operation phase
(2011), the numbers of Black-winged Stilt, Kentish plover, and Little tern declined
in impacted saltpans in relation to the expectation from temporal trends at control
saltpans (Table 12.1).
Black-Winged Stilt Nest Spatial Distribution Within the Saltpans
The total number of nests at the saltpans monitored showed a steady negative
temporal trend: annual average = 81.2 (density=22.3 nests/ha), 2006 = 97 (26.6
nests/ha), 2008 = 89 (22.6 nests/ha), 2009 = 81 (21.1 nests/ha), 2011 = 58 (17.5
nests/ha). Considering the four years, it was found that most of the Black-winged
Stilt nests were built in feeders (annual average = 32.2 nests) and evaporators (45.7
nests), while few were found in crystallizers (3.2 nests). There was no evidence of
the railway affecting nest numbers, as the full GLMM did not differ significantly
from the model without the interaction term (Table 12.1).
Black-Winged Stilt Breeding Phenology and Success
Overall, the nesting phenology of Black-winged stilts was clearly unimodal, with
the first nest detected in week 16 (late April) and the last on week 27 (early July),
with a peak number of nests in week 21 (end of May) (Fig. 12.3). There were no
significant differences in phenology between impacted and control in any phase, but
12 Evaluating the Impacts of a New Railway on Shorebirds …
205
activity with time (year) and type of saltpan (impacted and control) using a GLMM
with a binomial distribution function, controlling for saltpan area (Crawley 2013).
Results
Effects on Breeding Shorebirds
Shorebird Abundances
The average abundance of breeding shorebirds presented large variations, which
ranged from the complete absence in some saltpans, in a breeding season, to
maximum average values per saltpan of 36.2 Black-winged stilts (9.3 birds/ha),
26.0 Kentish plovers (7.9 birds/ha) and 89.7 Little terns (23.0 birds/ha) in 2006. For
the three focal species, there was a significant interaction term between time and
type of pond (Table 12.1), thus pointing out an impact of the construction and
operation of the railway viaduct. Regarding the construction phase, there were
significant increases in the abundance of Kentish plover (2008) and Little tern
(2008 and 2009) in impacted saltpans in relation to the expectation from temporal
trends at control saltpans (Table 12.1). However, during the operation phase
(2011), the numbers of Black-winged Stilt, Kentish plover, and Little tern declined
in impacted saltpans in relation to the expectation from temporal trends at control
saltpans (Table 12.1).
Black-Winged Stilt Nest Spatial Distribution Within the Saltpans
The total number of nests at the saltpans monitored showed a steady negative
temporal trend: annual average = 81.2 (density=22.3 nests/ha), 2006 = 97 (26.6
nests/ha), 2008 = 89 (22.6 nests/ha), 2009 = 81 (21.1 nests/ha), 2011 = 58 (17.5
nests/ha). Considering the four years, it was found that most of the Black-winged
Stilt nests were built in feeders (annual average = 32.2 nests) and evaporators (45.7
nests), while few were found in crystallizers (3.2 nests). There was no evidence of
the railway affecting nest numbers, as the full GLMM did not differ significantly
from the model without the interaction term (Table 12.1).
Black-Winged Stilt Breeding Phenology and Success
Overall, the nesting phenology of Black-winged stilts was clearly unimodal, with
the first nest detected in week 16 (late April) and the last on week 27 (early July),
with a peak number of nests in week 21 (end of May) (Fig. 12.3). There were no
significant differences in phenology between impacted and control in any phase, but
12 Evaluating the Impacts of a New Railway on Shorebirds …
205