Direct habitat measures |
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Food availability
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Prey animal biomass (Atiénzar et al., 2012, Deboelpaep et al., 2020,
Herring and Gawlik, 2013, Holopainen et al., 2014, Hunt et al., 2017,
Parks et al., 2016, Schultz et al., 2020)
Plant-derived food density or abundance (Arzel et al., 2015, Atiénzar
et al., 2012, Dugger and Feddersen, 2009)
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Birds behaviourally track sites with highest prey biomass and density
(Rose and Nol, 2010)
Prey availability has a positive influence on reproductive performance
(Herring et al., 2010)
Chick condition is related to local prey abundance (Hunt et al., 2017)
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Predicts occupancy but not abundance (Gillespie and Fontaine, 2017)
Sites with high food densities are not always the favoured foraging
sites (Hagy and Kaminski, 2015)
The seeds of different plant species consumed by waterfowl have
different energy content (Dugger et al., 2007)
Different food items can result in different mass gain even when fed
ad libitum (Jorde et al., 1995)
Waterbirds may forage selectively on larger size-class prey items
meaning that overall prey density is not reduced through waterbird
foraging even though waterbirds’ preferred prey size has been
significantly depleted (Fonseca and Navedo, 2020)
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Site/region – Instantaneous/within season/annual
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Primary productivity
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Normalised Difference Vegetation Index (NDVI) (Tang et al., 2016,
Zhang et al., 2017)
Enhanced Vegetation Index (EVI) (Guan et al., 2016)
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—
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The method provides an indirect indication of habitat quality with at
least one further transitional state before primary productivity
influences waterbird energy intake rate (Zhang et al., 2017)
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Site/region/Flyway – Instantaneous/within season/annual
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Predation pressure
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Predator track density (Cohen et al., 2009)
Index of predator reproduction (Trinder et al., 2009)
Proportion of radio-tracked individuals predated (Kenow et al., 2009,
Swift et al., 2020)
Proportion of real or fake nests predated (Pehlak and Lõhmus, 2008,
Swift et al., 2020)
Alternate prey density (Holopainen et al., 2014)
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Predation can be the leading cause of waterbird nest failure (Riecke
et al., 2019)
Predation risk is evaluated by waterbirds and trade-offs made that may
reduce other components of fitness (e.g., foraging rate) (Fernández
and Lank, 2010)
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Nest predation rate was not a function of predator abundance or the
availability of alternate prey species (Machín et al., 2019)
The influence of predation can differ depending of the waterbird
population density (Lebeuf and Giroux, 2014)
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Site/region – Instantaneous/within season/annual
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Vegetation structure
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Vegetation height (Barati et al., 2011)
Vegetation cover/abundance (Atiénzar et al., 2012, Hamza et al., 2015,
Hierl et al., 2007, Nyman and Chabreck, 1996)
Vegetation community composition (Benedict and Hepp, 2000, Dugger and
Feddersen, 2009)
Presence of invasive plants (Khan, 2010, Tavernia and Reed, 2012)
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Vegetation structure has implications for the suitability of a site
for nest placement (Barati et al., 2011)
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Dense vegetation may increase prey abundance but reduce prey capture
efficiency (Lantz et al., 2011)
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Site/region – Instantaneous/within season/annual
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Wetland spatial attributes
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Connectivity to neighbouring wetlands (Sebastián-González et al.,
2010b)
Pond area (Atiénzar et al., 2012, He et al., 2009, Merendino and
Ankney, 1994)
Shoreline irregularity (Merendino and Ankney, 1994)
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Pond size and distance to the nearest neighbouring wetland are
important determinants of waterbird habitat selection
(Sebastián-González et al., 2010b)
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Cycles of hydrological stress (drought/non-drought) can influence
waterfowl habitat preferences, with birds seeking relatively deeper
water bodies during drought irrespective of other habitat variables
that are influential in wet years (Atiénzar et al., 2012)
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Site/region – Instantaneous/within season/annual
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Water level
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Drawdown (Herring and Gawlik, 2013, Townsend et al., 2006);
Water level variability (Collazo et al., 2002)
Availability of shallow water (Collazo et al., 2002, Gawlik and
Crozier, 2007, Lantz et al., 2011)
Landscape depth heterogeneity (Beerens et al., 2015)
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Wading birds preferentially selected ponds that had been
experimentally manipulated to have shallow rather than deep water
(Gawlik and Crozier, 2007) and waterbird species richness and density
correlates with the availability of shallow water habitats (Wang and
So, 2003)
Water level recession rate was a key influence on physiological
condition of two species of waterbirds (Herring and Gawlik, 2013)
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Water level variability did not influence habitat selection of wading
birds (Gawlik and Crozier, 2007)
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Site/region – Instantaneous/within season/annual
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Disturbance
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Distance to footpaths, roads, or railways (Burton et al., 2002, Hu et
al., 2016, Li et al., 2019)
Human settlements (Li et al., 2019)
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The presence of people and vehicles nearby (≤50 m) reduces foraging
rates (Maslo et al., 2012) Likewise, time spent foraging and flock
density were reduced at a highly disturbed site (Swift et al., 2020)
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Human activities (e.g., clam harvesting) may have positive effects on
waterbirds, especially shorebirds (Hamza et al., 2015)
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Site/region – Instantaneous/within season/annual
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Foraging substrate
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Sediment grain size (Reurink et al., 2015, Rose and Nol, 2010)
Organic carbon content (Hamza et al., 2015, Reurink et al., 2015)
Mud content (Hamza et al., 2015)
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Prey biomass is strongly predicted by physical environment conditions
including organic content and particle sizes of the sediments (Rose
and Nol, 2010)
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Site/region – Instantaneous/within season/annual
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Land use
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Proportion of agricultural land use (Austin et al., 2001, Duncan et
al., 1999)
Mariculture (Li et al., 2019)
Mining (Li et al., 2019)
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Changing land use can cause ecological traps if agricultural
landscapes appear similar to natural landscapes (e.g., grasslands) but
offer lower habitat quality (Buderman et al., 2020)
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Factors such as traditional site use by waterbirds can confound the
signal of change in response to changing land use (Tombre et al.,
2005)
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Site/region – Instantaneous/within season/annual
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Water chemistry
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Colour/turbidity (Atiénzar et al., 2012, Merendino and Ankney, 1994)
pH (Merendino and Ankney, 1994, Walsh et al., 2006)
Conductivity/salinity (Atiénzar et al., 2012, Merendino and Ankney,
1994)
Dissolved nutrients (Merendino and Ankney, 1994, Pöysä et al., 2001,
Walsh et al., 2006)
Chlorophyll-α concentration (Atiénzar et al., 2012)
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Prey biomass is influenced by salinity (Rose and Nol, 2010)
Water chemistry variables including pH, salinity, and nitrogen and
potassium concentration can be a predictor of occurrence of breeding
ducks (Walsh et al., 2006)
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Site/region – Instantaneous/within season/annual
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Bird-derived estimates |
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Demographic measures |
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Reproduction
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Clutch size/volume (Hunt et al., 2017, Mallory et al., 1994, Powell
and Powell, 1986)
Number of fledglings (Powell and Powell, 1986)
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A direct contributor to the per capita rate of population increase,
the most proximate indicator of habitat quality
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Site/region – Instantaneous/within season/annual
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Survival
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Adult survival (Alves et al., 2013, Rice et al., 2007, Swift et al.,
2020)
Brood survival (Aubry et al., 2013, Cohen et al., 2009, Hunt et al.,
2017, Owen and Pierce, 2014, Simpson et al., 2007, Swift et al., 2020)
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A direct contributor to the per capita rate of population increase,
the most proximate indicator of habitat quality
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Site/region – Instantaneous/within season/annual
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Distributional measures |
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Density or abundance
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Abundance (Castillo-Guerrero et al., 2009, Dugger and Feddersen, 2009,
Ganzevles and Bredenbeek, 2005, Hickman, 1994, Liu et al., 2006)
Species richness (Dugger and Feddersen, 2009, Hickman, 1994)
Density (Loewenthal et al., 2015, Swift et al., 2020)
Abundance of breeding pairs (Arzel et al., 2015, Austin et al., 2001,
Sebastián-González et al., 2010a)
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The density of breeding pairs increased much faster than could be
explained by population growth rates following habitat management that
resulted in greater food availability (Loewenthal et al., 2015) This
was attributed to previously subordinate adults taking up breeding
territories as territory size of existing pairs contracted (Loewenthal
et al., 2015)
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Can be confounded by site fidelity (O’Neil et al., 2014), lags in
response to change in condition (Loewenthal et al., 2015, Meltofte,
2006), dispersal barriers or costs, and imperfect knowledge of habitat
(Lewis et al., 2010)
Local and regional weather influences habitat use (Kelly, 2001,
Schummer et al., 2010)
Reproductive output is not correlated with population density (Cohen
et al., 2009)
Reduction in food availability can increase shorebird density as they
are concentrated into the remaining suitable patches (Kosztolányi et
al., 2006)
Disturbance by human activity and farming rather than habitat quality
(availability of foraging areas) more strongly influences waterbird
species richness and abundance (Quan et al., 2002)
Requires birds to correctly perceive habitat cues, which may not
always be the case (e.g., agricultural land uses may resemble native
grasslands, but have much lower reproductive output) (Buderman et al.,
2020)
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Site/region – Instantaneous/within season/annual
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Phenology
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Length of breeding period (Raquel et al., 2016)
Residence times on non-breeding or stopover sites (O’Neal et al.,
2012, Rice et al., 2007, Williams et al., 2019)
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Spring migration stopover duration can decrease as a function of
Julian day of the year (Williams et al., 2019)
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Site/region –Within season/annual
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Age class distribution
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Age class distribution (Fernández and Lank, 2010)
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Adult shorebirds occupy sites with greater prey availability and lower
predation risk than immature birds (Fernández and Lank, 2006)
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Site/region – Instantaneous/within season
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Hunting records
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Harvest numbers as an indicator of present and past habitat quality
(Merendino et al., 1992)
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Region – Annual
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Individual condition measures |
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Morphological variables
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Abdominal profile index (Swift et al., 2020)
Body mass (Herring and Gawlik, 2013, Hunt et al., 2017)
Body condition index (Aubry et al., 2013, Parks et al., 2016)
Chick growth rate (Hunt et al., 2017, Owen and Pierce, 2014)
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Abdominal profile index on the non-breeding grounds was correlated
with breeding ground return rates, and subsequent nest survival and
chick fate (Swift et al., 2020)
Chick growth rates and adult body mass were positively correlated with
invertebrate abundance in breeding Piping Plovers (Hunt et al., 2017)
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Site/region –Within season/annual
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Physiological variables
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Stress markers (Aharon-Rotman et al., 2016b, Herring and Gawlik, 2013,
Thomas and Swanson, 2013)
Immune response markers (Buehler et al., 2009)
Foraging metabolites (Lyons et al., 2008, Thomas and Swanson, 2013)
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Birds that occupy sites with higher fueling rates have lower
concentration of physiological markers of stress in their blood
(Aharon-Rotman et al., 2016b)
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Different species with different foraging strategies can have
different blood physiology responses to changing availability of prey
(Herring and Gawlik, 2013)
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Site/region –Within season/annual
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Parasite burden
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Intestinal helminth load (Conner England et al., 2018)
Haemosporidian parasite infection (Aharon-Rotman et al., 2016b)
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Parasite burden negatively correlated with foraging habitat quality
for some parasite taxa, but not significantly for all parasite taxa
(Conner England et al., 2018)
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Site/region –Within season/annual
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Ptilochronology
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Feather growth rate (Swift et al., 2020)
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Width of feather growth bands was positively correlated with an index
of body condition (abdominal profile index) and feeding rates (Swift
et al., 2020)
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Site/region –Within season/annual
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Behavioural measures |
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Foraging parameters
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Peck/probe rate (Castillo-Guerrero et al., 2009, Mander et al., 2013)
Success rate (Castillo-Guerrero et al., 2009, Swift et al., 2020)
Step rate during foraging (Mander et al., 2013)
Energy intake rate (Yu et al., 2020)
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Positively correlated with prey density and biomass and at productive
sites may not be affected by interference competition (Rose and Nol,
2010)
Peck rate is correlated with defecation rate indicating that peck rate
is a meaningful proxy for intake rate (Rose and Nol, 2010)
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Capture success can be influenced by conspecifics, with increases in
capture success occurring until conspecific density becomes high
enough to induce interference competition (Stolen et al., 2012)
Peck rate also reaches an upper asymptote, so may not be a true
indication of habitat quality in very high productivity landscapes
(Rose and Nol, 2010)
Pecking rate can be significantly higher than probing rate for an
equivalent energy return (Kuwae et al., 2010)
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Site/region – Instantaneous/within season/annual
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Time budgets
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Proportion of time spent foraging (Castillo-Guerrero et al., 2009,
Dugger and Feddersen, 2009, van der Kolk et al., 2019)
Proportion of time in non-foraging behaviours (e.g., vigilance,
disturbance) (Castillo-Guerrero et al., 2009, Maslo et al., 2012, Yu
et al., 2020)
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Oystercatchers that spent longer foraging had lower inferred survival
(van der Kolk et al., 2019)
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Time budgets may vary within an individual period of the annual cycle
(e.g., between breeding stages, or within the non-breeding period)
(Castillo-Guerrero et al., 2009, Mallory et al., 1999) or due to the
presence of conspecifics (Kosztolányi et al., 2006, Mallory et al.,
1999)
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Site/region – Instantaneous/within season/annual
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Anti-predator behaviours
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Vigilance rates (Fernández and Lank, 2010)
Flight initiation distance (Gunness et al., 2001)
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At sites where vigilance rates were higher, waterbirds maintained
lower body mass (Fernández and Lank, 2010)
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Site/region – Instantaneous/within season/annual
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Individual movements
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Home range size (Herring and Collazo, 2005)
Commuting distance (Custer et al., 2004)
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Site/region – Instantaneous/within season/annual
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Flight speeds
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Flight speeds between foraging patches (Reurink et al., 2015)
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Birds fly faster when heading to patches of high prey abundance
because the greater expected returns are able to offset the greater
flight costs of choosing to fly faster (Reurink et al., 2015)
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Requires the birds to have perfect knowledge of the resource
distribution available (Reurink et al., 2015), which may not always be
the case (Lewis et al., 2010)
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Site/region – Instantaneous/within season/annual
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