CHAPTER10 General discussion STRUGGLE FOR SAFETY: ADAPTIVE RESPONSES OF WINTERING WADERS TO THEIR... more CHAPTER10 General discussion STRUGGLE FOR SAFETY: ADAPTIVE RESPONSES OF WINTERING WADERS TO THEIR AVIAN PREDATORS Piet J. van den Hout Showing in more detail why falcons would not be able to regulate shorebird populations by killing themthen explaining how ...
Data are provided for: Fig. 2 panels a (avgHUdfs10.txt) and b (vigilance_largescale.txt): vigilan... more Data are provided for: Fig. 2 panels a (avgHUdfs10.txt) and b (vigilance_largescale.txt): vigilance as a function of distance from shore; Fig. 3: Number of individuals that were observed in nearshore dangerous and offshore safe habitat, shown for the 40 m (ch.knots.40m.txt ) and 500 m (ch.knots.500m.txt) danger zone boundaries; for the Multi-state mark-recapture analyses with use of the RMark package, including fig. 4(cr.knots.May2015.txt
In most birds, flight is the most important means of escape from predators. Impaired flight abili... more In most birds, flight is the most important means of escape from predators. Impaired flight abilities due to increased wing loading may increase vulnerability to predation. To compensate for an increase in wing loading, birds are able to independently decrease body mass (BM) or increase pectoral muscle mass (PMM). Comparing nearshore and farshore foraging shorebird species, we develop a theory as to which of these responses should be the most appropriate. We hypothesize that nearshore foragers should respond to increased predation by increasing their PMM in order to promote speed-based escape. Instead, farshore foragers should decrease BM in order to improve agility for maneuvering escape. Experiments on 2 shorebird species are consistent with these predictions, but on the basis of the theoretical framework for evaluating effect size and biological significance developed here, more experiments are clearly needed.
Editorial Mark A Elgar 1 Sex matters: a social context to boldness in guppies (Poecilia reticulat... more Editorial Mark A Elgar 1 Sex matters: a social context to boldness in guppies (Poecilia reticulata) Chantima Piyapong, Jens Krause, Ben B. Chapman, Indar W. Ramnarine, Vasilis Louca, and Darren P. Croft 3 Reduced extrapair paternity in response to experimental stimulation of earlier incubation onset in blue tits Oscar Vedder, Michael JL Magrath, Anna MF Harts, Elske Schut, Marco van der Velde, and Jan Komdeur 9 Predator escape tactics in birds: linking ecology and aerodynamics Piet J. van den Hout, Kimberley J. Mathot, Leo RM Maas, and Theunis ...
At the start of the 21st century the majority of migratory wader (shorebird) populations are face... more At the start of the 21st century the majority of migratory wader (shorebird) populations are faced with serious threats. This commonly results from the continuous destruction of wetlands, their key habitat. Healthy wetlands are highly biodiverse and extremely vulnerable, and as functioning ecosystems particularly important for us humans for a sustained livelihood (artisanal fisheries, small-scale farming) and our well-being (effective water filtering and cleaning systems). In many parts of the world, wetlands have been seen as wastelands, or even as a source of threat (malaria). Many freshwater wetlands have been drained for agricultural use and mudflats have been reclaimed for settlement and urbanization. Wetlands are continuously squeezed by economic development and increasingly used for recreational activities, and their resources are, in general, notoriously overexploited.
Observers tend to derive the direction of attention of a scan from the head posture of the bird, ... more Observers tend to derive the direction of attention of a scan from the head posture of the bird, and a tilted position of the head is commonly interpreted as scanning the sky for predators. However, contrary to humans, many birds have two or more areas in each retina that are specialized for high-acuity vision. This implies that, particularly in monocular vision, head angle may not always reliably tell us were a bird’s attention is actually directed or what part of the visual scene the bird is examining in detail. We report insightful observations on extreme head tilting behaviours in two shorebird species, Baird’s Sandpiper Calidris bairdii and Puna Plover Charadrius alticola foraging at midday, and under a clear sky, on a salt plain in Chile. From the viewpoint that careful interpretation of head postures is essential when studying anti-predation vigilance of foragers, we discuss whether such head postures may be a manifestation of a particular type of vigilance behaviour whose pr...
Mass regulation in birds is well documented. For example, birds can increase body mass in respons... more Mass regulation in birds is well documented. For example, birds can increase body mass in response to lower availability and/or predictability of food and decrease body mass in response to increased predation danger. Birds also demonstrate an ability to maintain body mass across a range of food qualities. Although the adaptive significance of mass regulation has received a great deal of theoretical and empirical attention, the mechanisms by which birds achieve this have not. Several non-exclusive mechanisms could facilitate mass regulation in birds. Birds could regulate body mass by adjusting food intake (dieting), activity, baseline energetic requirements (basal metabolic rate), mitochondrial efficiency or assimilation efficiency. Here, we present the results of two experiments in captive red knots (Calidris canutus islandica) that assess three of these proposed mechanisms: dieting, activity and up- and down-regulation of metabolic rate. In the first experiment, knots were exposed ...
Metawad is a five-year research project funded by Waddenfonds that started in 2011. One of its ai... more Metawad is a five-year research project funded by Waddenfonds that started in 2011. One of its aims is to investigate how population changes of migrating shorebirds are driven by changes in the conditions in their main feeding habitat, intertidal mudflats. We investigate how differences in survival may be preceded by differences in behavioural indicators related to foraging, which in turn may be driven by factors like food, forager density and distribution, and predation danger. Metawad focuses on five long-distance migrant species differing in feeding habits and migration routines: Brent Goose Branta bernida, Eurasian Spoonbill Platalea leucorodia, Bar-tailed Godwit Limosa lapponica, Red Knot Calidris canutus and Sander-ling Calidris alba. To put the data on these target species in a wider context, we started off by mapping the low tide distribution of a wider array of shorebird species in the Dutch Wadden Sea, with the aim to link this (at a later stage) to available food stocks, ...
Overwintering Coots Fulica atra atra were observed in January 2006, in Keoladeo National Park, In... more Overwintering Coots Fulica atra atra were observed in January 2006, in Keoladeo National Park, India. Here they fed on aquatic plants, which they exploited in strictly-maintained dense flotillas; these flocks behaved like a super-organism. This observation adds to a description of Ali & Ripley (1969), who do not explicitly discuss the cause of raft formation by Coots, but only mention the occurrence of Coot predation by Greater Spotted Eagle Aquila clanga. Having observed a Coot being drowned by a Ganges Soft-shell Turtle Aspideretus gangeticus, I suggest that predation risk by these turtles should be taken into account as a possible cause for this herding behaviour. When on the water, Coot flocks now and then suddenly scattered; this suggested disturbance by a hidden aquatic predator, all the more because no raptor attacks were witnessed on these occasions. Coots visited the water exclusively for foraging, and, in contrast to their usual behaviour, roosted on islands. This indicate...
... Likewise, flocks tend to roost on open water (Cramp & Simmons 1993, Bijlsma et al. 2001),... more ... Likewise, flocks tend to roost on open water (Cramp & Simmons 1993, Bijlsma et al. 2001), and when feeding, if not on water, they mostly do so near the water's edge, ensuring escape routes towards the water (Glutz von Blotzheim et al. 1973, Irwin & O'Halloran 1997). ...
CHAPTER10 General discussion STRUGGLE FOR SAFETY: ADAPTIVE RESPONSES OF WINTERING WADERS TO THEIR... more CHAPTER10 General discussion STRUGGLE FOR SAFETY: ADAPTIVE RESPONSES OF WINTERING WADERS TO THEIR AVIAN PREDATORS Piet J. van den Hout Showing in more detail why falcons would not be able to regulate shorebird populations by killing themthen explaining how ...
Data are provided for: Fig. 2 panels a (avgHUdfs10.txt) and b (vigilance_largescale.txt): vigilan... more Data are provided for: Fig. 2 panels a (avgHUdfs10.txt) and b (vigilance_largescale.txt): vigilance as a function of distance from shore; Fig. 3: Number of individuals that were observed in nearshore dangerous and offshore safe habitat, shown for the 40 m (ch.knots.40m.txt ) and 500 m (ch.knots.500m.txt) danger zone boundaries; for the Multi-state mark-recapture analyses with use of the RMark package, including fig. 4(cr.knots.May2015.txt
In most birds, flight is the most important means of escape from predators. Impaired flight abili... more In most birds, flight is the most important means of escape from predators. Impaired flight abilities due to increased wing loading may increase vulnerability to predation. To compensate for an increase in wing loading, birds are able to independently decrease body mass (BM) or increase pectoral muscle mass (PMM). Comparing nearshore and farshore foraging shorebird species, we develop a theory as to which of these responses should be the most appropriate. We hypothesize that nearshore foragers should respond to increased predation by increasing their PMM in order to promote speed-based escape. Instead, farshore foragers should decrease BM in order to improve agility for maneuvering escape. Experiments on 2 shorebird species are consistent with these predictions, but on the basis of the theoretical framework for evaluating effect size and biological significance developed here, more experiments are clearly needed.
Editorial Mark A Elgar 1 Sex matters: a social context to boldness in guppies (Poecilia reticulat... more Editorial Mark A Elgar 1 Sex matters: a social context to boldness in guppies (Poecilia reticulata) Chantima Piyapong, Jens Krause, Ben B. Chapman, Indar W. Ramnarine, Vasilis Louca, and Darren P. Croft 3 Reduced extrapair paternity in response to experimental stimulation of earlier incubation onset in blue tits Oscar Vedder, Michael JL Magrath, Anna MF Harts, Elske Schut, Marco van der Velde, and Jan Komdeur 9 Predator escape tactics in birds: linking ecology and aerodynamics Piet J. van den Hout, Kimberley J. Mathot, Leo RM Maas, and Theunis ...
At the start of the 21st century the majority of migratory wader (shorebird) populations are face... more At the start of the 21st century the majority of migratory wader (shorebird) populations are faced with serious threats. This commonly results from the continuous destruction of wetlands, their key habitat. Healthy wetlands are highly biodiverse and extremely vulnerable, and as functioning ecosystems particularly important for us humans for a sustained livelihood (artisanal fisheries, small-scale farming) and our well-being (effective water filtering and cleaning systems). In many parts of the world, wetlands have been seen as wastelands, or even as a source of threat (malaria). Many freshwater wetlands have been drained for agricultural use and mudflats have been reclaimed for settlement and urbanization. Wetlands are continuously squeezed by economic development and increasingly used for recreational activities, and their resources are, in general, notoriously overexploited.
Observers tend to derive the direction of attention of a scan from the head posture of the bird, ... more Observers tend to derive the direction of attention of a scan from the head posture of the bird, and a tilted position of the head is commonly interpreted as scanning the sky for predators. However, contrary to humans, many birds have two or more areas in each retina that are specialized for high-acuity vision. This implies that, particularly in monocular vision, head angle may not always reliably tell us were a bird’s attention is actually directed or what part of the visual scene the bird is examining in detail. We report insightful observations on extreme head tilting behaviours in two shorebird species, Baird’s Sandpiper Calidris bairdii and Puna Plover Charadrius alticola foraging at midday, and under a clear sky, on a salt plain in Chile. From the viewpoint that careful interpretation of head postures is essential when studying anti-predation vigilance of foragers, we discuss whether such head postures may be a manifestation of a particular type of vigilance behaviour whose pr...
Mass regulation in birds is well documented. For example, birds can increase body mass in respons... more Mass regulation in birds is well documented. For example, birds can increase body mass in response to lower availability and/or predictability of food and decrease body mass in response to increased predation danger. Birds also demonstrate an ability to maintain body mass across a range of food qualities. Although the adaptive significance of mass regulation has received a great deal of theoretical and empirical attention, the mechanisms by which birds achieve this have not. Several non-exclusive mechanisms could facilitate mass regulation in birds. Birds could regulate body mass by adjusting food intake (dieting), activity, baseline energetic requirements (basal metabolic rate), mitochondrial efficiency or assimilation efficiency. Here, we present the results of two experiments in captive red knots (Calidris canutus islandica) that assess three of these proposed mechanisms: dieting, activity and up- and down-regulation of metabolic rate. In the first experiment, knots were exposed ...
Metawad is a five-year research project funded by Waddenfonds that started in 2011. One of its ai... more Metawad is a five-year research project funded by Waddenfonds that started in 2011. One of its aims is to investigate how population changes of migrating shorebirds are driven by changes in the conditions in their main feeding habitat, intertidal mudflats. We investigate how differences in survival may be preceded by differences in behavioural indicators related to foraging, which in turn may be driven by factors like food, forager density and distribution, and predation danger. Metawad focuses on five long-distance migrant species differing in feeding habits and migration routines: Brent Goose Branta bernida, Eurasian Spoonbill Platalea leucorodia, Bar-tailed Godwit Limosa lapponica, Red Knot Calidris canutus and Sander-ling Calidris alba. To put the data on these target species in a wider context, we started off by mapping the low tide distribution of a wider array of shorebird species in the Dutch Wadden Sea, with the aim to link this (at a later stage) to available food stocks, ...
Overwintering Coots Fulica atra atra were observed in January 2006, in Keoladeo National Park, In... more Overwintering Coots Fulica atra atra were observed in January 2006, in Keoladeo National Park, India. Here they fed on aquatic plants, which they exploited in strictly-maintained dense flotillas; these flocks behaved like a super-organism. This observation adds to a description of Ali & Ripley (1969), who do not explicitly discuss the cause of raft formation by Coots, but only mention the occurrence of Coot predation by Greater Spotted Eagle Aquila clanga. Having observed a Coot being drowned by a Ganges Soft-shell Turtle Aspideretus gangeticus, I suggest that predation risk by these turtles should be taken into account as a possible cause for this herding behaviour. When on the water, Coot flocks now and then suddenly scattered; this suggested disturbance by a hidden aquatic predator, all the more because no raptor attacks were witnessed on these occasions. Coots visited the water exclusively for foraging, and, in contrast to their usual behaviour, roosted on islands. This indicate...
... Likewise, flocks tend to roost on open water (Cramp & Simmons 1993, Bijlsma et al. 2001),... more ... Likewise, flocks tend to roost on open water (Cramp & Simmons 1993, Bijlsma et al. 2001), and when feeding, if not on water, they mostly do so near the water's edge, ensuring escape routes towards the water (Glutz von Blotzheim et al. 1973, Irwin & O'Halloran 1997). ...
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