Abstract:SignificanceProcellariiform seabirds homing from distant foraging locations present a natural situation in which the homing route can become obstructed by islands or peninsulas because birds will not travel long distances over land. By measuring initial orientation from Global Positioning System (GPS) tracks during homing, we found that the Manx shearwater fails to encode such obstacles while homing, implying a navigation system that encodes the direction of home rather than a learned route. Nonetheless, shear… Show more
“…The tracks of all displaced birds are shown in figure 2 a,b . Figure 2The tracks of released birds that go the short route ( a ) and long route ( b ) around the island of Ireland are shown; ( c ) shows the homing trips of free-ranging shearwaters (17 trips from 16 birds) hitting the coast of Ireland and proceeding via the short route on their homing journeys [2,3]. …”
Section: Resultsmentioning
confidence: 99%
“…Manx shearwaters, Puffinus puffinus , and other procellariform seabirds do not routinely travel large distances over land [1]. In this system, topographic features, such as islands and peninsulas, create natural barriers in the environment that present contrasts between the shortest flyable route (over only water) and the direction home notwithstanding the obstacle (henceforth beeline, [2,3]). If homing is guided by true navigation (TN), navigation from beyond sensory contact with a goal and without the requirement for experience from that specific location using exocentric sensory cues [4,5], then this might be indicated when birds are unable to use knowledge of available routes that are more efficient than the beeline home.…”
Section: Introductionmentioning
confidence: 99%
“…When homing after foraging, free-ranging Manx shearwaters, on average, orient initially along with the beeline even from places where the beeline route is blocked by an island or peninsula, suggesting they use TN to encode a direction home without local route knowledge [2,3]. Several important features of this long-range navigation system remain unknown, however.…”
The cognitive processes (learning and processing of information) underpinning the long-distance navigation of birds are poorly understood. Here, we used the homing motivation of the Manx shearwater to investigate navigational decision making in a wild bird by displacing them 294 km to the far side of a large island (the island of Ireland). Since shearwaters are reluctant to fly over land, the island blocked the direct route home, forcing a navigational decision. Further still, on the far side of the obstacle, we chose a release site where the use of local knowledge could facilitate a 20% improvement in route efficiency if shearwaters were able to anticipate and avoid a large inlet giving the appearance of open water in the home direction. We found that no shearwater took the most efficient initial route home, but instead oriented in the home direction (even once the obstacle became visible). Upon reaching the obstacle, four shearwaters subsequently circumnavigated the land mass via the long route, travelling a further 900 km as a result. Hence, despite readily orienting homewards immediately after displacement, shearwaters seem unaware of the scale of the obstacle formed by a large land mass despite this being a prominent feature of their regular foraging environment.
“…The tracks of all displaced birds are shown in figure 2 a,b . Figure 2The tracks of released birds that go the short route ( a ) and long route ( b ) around the island of Ireland are shown; ( c ) shows the homing trips of free-ranging shearwaters (17 trips from 16 birds) hitting the coast of Ireland and proceeding via the short route on their homing journeys [2,3]. …”
Section: Resultsmentioning
confidence: 99%
“…Manx shearwaters, Puffinus puffinus , and other procellariform seabirds do not routinely travel large distances over land [1]. In this system, topographic features, such as islands and peninsulas, create natural barriers in the environment that present contrasts between the shortest flyable route (over only water) and the direction home notwithstanding the obstacle (henceforth beeline, [2,3]). If homing is guided by true navigation (TN), navigation from beyond sensory contact with a goal and without the requirement for experience from that specific location using exocentric sensory cues [4,5], then this might be indicated when birds are unable to use knowledge of available routes that are more efficient than the beeline home.…”
Section: Introductionmentioning
confidence: 99%
“…When homing after foraging, free-ranging Manx shearwaters, on average, orient initially along with the beeline even from places where the beeline route is blocked by an island or peninsula, suggesting they use TN to encode a direction home without local route knowledge [2,3]. Several important features of this long-range navigation system remain unknown, however.…”
The cognitive processes (learning and processing of information) underpinning the long-distance navigation of birds are poorly understood. Here, we used the homing motivation of the Manx shearwater to investigate navigational decision making in a wild bird by displacing them 294 km to the far side of a large island (the island of Ireland). Since shearwaters are reluctant to fly over land, the island blocked the direct route home, forcing a navigational decision. Further still, on the far side of the obstacle, we chose a release site where the use of local knowledge could facilitate a 20% improvement in route efficiency if shearwaters were able to anticipate and avoid a large inlet giving the appearance of open water in the home direction. We found that no shearwater took the most efficient initial route home, but instead oriented in the home direction (even once the obstacle became visible). Upon reaching the obstacle, four shearwaters subsequently circumnavigated the land mass via the long route, travelling a further 900 km as a result. Hence, despite readily orienting homewards immediately after displacement, shearwaters seem unaware of the scale of the obstacle formed by a large land mass despite this being a prominent feature of their regular foraging environment.
“…However, these rafts form for only a few hours and consist of many thousands of shearwaters, and we did not find evidence for individuals rafting in consistent locations (Supporting information), making this hypothesis unlikely. Furthermore, it has been previously observed that shearwaters returning from long, selfâmaintenance trips tend to return to the nest immediately following their commute, rather than spending any time rafting (Padget et al 2019). Consequently, they are likely to return to the nest immediately following their foraging trip, eliminating the possibility of meeting their partner in the waters around the colony.…”
Many species that provide care for their offspring in tandem with a partner coordinate their activities to maximise the efficiency of their investment. However, it is not well known exactly how this coordination is achieved. Manx shearwaters Puffinus puffinus are Procellariiform seabirds that exhibit a dual foraging strategy during chick provisioning in which long foraging trips to maintain condition are alternated with short, frequent trips to feed the offspring. This strategy is employed in a coordinated manner between the parents, with one making short trips while the other takes a single long trip. Previous work revealed that a complementary switch in foraging trip type is initiated by the parents following a synchronous visit to the nest. We used a combination of observational data and experimental manipulation to examine the mechanisms that may underlie this behaviour. Specifically, we investigated the evidence that physical reunion is necessary to induce a switch in trip type, whether parents change their behaviour to maximise the probability of partner encounter, and whether indirect cues gained from the chick could inform a switch in behaviour. In our experimental approach, we manipulated the information adults had available to them by supplementarily feeding chicks to alter their begging behaviour. We found no support for the role of physical reunion or indirect cues in the coordination of care in this species. We discuss the possibility that the patterns of alternated provisioning observed during chick rearing in Manx shearwaters may emerge through entrainment during the wellâcoordinated incubation period preceding chick provisioning.
“…In Figure 5 we provide a schematic proposing possible spatial scales at which key sensory modalities (vision, olfaction, magnetoreception, hearing) and proposed infrasound scenarios may be used by seabirds to obtain spatial information. Some seabird species home in a straight line (Catard and Weimerskirch, 1999, movement data drawn as Figure 2 in Benhamou et al, 2003;Padget et al, 2019), and because infrasound is not influenced by surface-level wind fields to the same degree as odour plumes, birds could use an infrasound beacon over large spatial scales, provided that they are able to identify the direction of the sound source and where this source is located close to the goal (Figure 4A). However, there are several limitations with a directional hearing mechanism along these lines, given seabird flight speeds and interaural time differences (see section "Can Infrasound be Detected by Birds?").…”
Section: How Might Seabirds Use Infrasound For Navigation?mentioning
Seabirds are amongst the most mobile of all animal species and spend large amounts of their lives at sea. They cross vast areas of ocean that appear superficially featureless, and our understanding of the mechanisms that they use for navigation remains incomplete, especially in terms of available cues. In particular, several large-scale navigational tasks, such as homing across thousands of kilometers to breeding sites, are not fully explained by visual, olfactory or magnetic stimuli. Low-frequency inaudible sound, i.e., infrasound, is ubiquitous in the marine environment. The spatio-temporal consistency of some components of the infrasonic wavefield, and the sensitivity of certain bird species to infrasonic stimuli, suggests that infrasound may provide additional cues for seabirds to navigate, but this remains untested. Here, we propose a framework to explore the importance of infrasound for navigation. We present key concepts regarding the physics of infrasound and review the physiological mechanisms through which infrasound may be detected and used. Next, we propose three hypotheses detailing how seabirds could use information provided by different infrasound sources for navigation as an acoustic beacon, landmark, or gradient. Finally, we reflect on strengths and limitations of our proposed hypotheses, and discuss several directions for future work. In particular, we suggest that hypotheses may be best tested by combining conceptual models of navigation with empirical data on seabird movements and in-situ infrasound measurements.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citationsâcitations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
