Third, our propeller loggers provide data on several behavioural parameters, such as acceleration, in addition to flight air speed. where is the profile power coefficient for this model (dimensionless). This work was funded by the program Bio-logging Science of the University of Tokyo (UTBLS), Grant-in-Aids for Scientific Research from the Japan Society for the Promotion of Science (JSPS) (21681002 to Y.Y.W., 20310016 to A.T. and 19255001 to K.S.) Cormorants’ feathers instead get waterlogged, allowing the bird to sink and dive more efficiently. The new research, published in the Journal of the Royal Society Interface, studied how cormorants and other diving birds are able to reach depths of some 30 meters without having water permanently wet their protective feathers. These calculations show that the estimate for Vmp is indeed sensitive to the change of flight angle. Flights were short (mean 92 s), with a mean summed duration of only 24 min day–1. Moreover, the measured flight air speeds were close to Vmp and lower than Vmr, especially when the Pennycuick model (Pennycuick, 2008) was applied. Data loggers in this study weighed 2.8% of the birds' body mass on average, which is relatively large and could potentially impact their flight and diving behaviour. The propeller loggers in air mode were set in front of the tunnel, and air speed was increased from 3 to 24 m s–1 with an increment of 3 m s–1. They can dive under water for more than a minute,reaching depths of around 10 metres. Below the water they swim byusing paddle movements of their feet which have a webbed membrane betweenthe four toes. Wing-propelled swimming, observed in auks, diving petrels and some shearwaters, is an evolutionary solution for the conflict of muscle allocation; however, these birds face other conflicts, including the design of wings (which cannot be efficient in both air and water) (Pennycuick, 2008) and the myoglobin concentration in the locomotor muscles (Croll et al., 1992; Davis and Guderley, 1987). flight duration, distance and speed) are still immature. 4). 2). Short wings are disadvantageous for flapping flight because of increased induced power (see Eqn 3). are reported. A major limitation in testing the prediction of evolutionary trade-offs is that, although the methods to record the diving behaviour of seabirds (e.g. Each trip consisted of the periods of flight, stay at the sea surface and diving (Fig. To interpret the measured flight air speed, the theoretical U-shaped curve that represents relationship between the mechanical power requirement and flight speed is useful (Tobalske, 2007; Pennycuick, 2008). Therefore, recording flight air speed continuously with other behavioural parameters using animal-attached tags would be a promising approach to better understand the flight behaviour of birds. Moreover, the relationship between dive depth and duration observed in this study (data not shown) closely resembled that reported previously with smaller data loggers (30 g) for the same species (Cook et al., 2008). Several types of data loggers (Little Leonardo Corp., Tokyo, Japan) were used (Table 1): M190L-D2GT (15 mm diameter, 53 mm in length, 16 g in air) recorded depth, two-axis accelerations and temperature; W190L-PD2GT (21 mm diameter, 117 mm in length, 60 g in air) recorded swim or flight speed (see below), depth, two-axis accelerations and temperature; W1000-PD3GT (22 mm in diameter, 102 mm length, 90 g in air) recorded swim or flight speed, depth, three-axis accelerations and temperature; and GPL20 [49 mm in width and length, 21 mm in depth (with rounded corners), 61 g in air] recorded GPS positions. Recently, several methods to record flight duration were developed (Dall'Antonia et al., 2001; Tremblay et al., 2003; Pelletier et al., 2008; Sato et al., 2008), and support for the prediction was provided: when two species of auks were compared, the species that flew for longer durations dived shallower and for shorter durations than the other (Thaxter et al., 2010). area of both wings including the part of the body between the wings, projected on a flat surface). In this study, we used newly developed tags to obtain detailed records of free-ranging flight behaviour as well as diving behaviour for a cormorant (here ‘cormorant’ is the general term for species in the family Phalacrocoracidae, whereas some of them are specifically called ‘shags’) (see Siegel-Causey, 1988). the power needed to overcome the drag of the wings). At 24 m s–1, it rotated continuously, but the rotation values recorded were very low, indicating that it idled relative to the shaft. Diving behaviour was recorded for 25 birds, with a grand mean dive depth of 27.7 m (max. In future work, the team will study the feathers of birds that can dive even deeper than cormorants, including penguins and auks. Moreover, the effect of off-axis flow was examined with the tunnel at an air speed of 12 m s–1 (close to the flight speed of shags; see Results) by setting the logger at an angle of 0 (head wind) to 90 deg (side wind) from the wind direction, with an increment of 10 deg. “Let’s say you make a hydrophobic surface so that even if it wets, by designing it the right way, just by shaking it the water might spontaneously dewet, and it would be dry again.”, The MIT analysis showed that this process only works with water. In the case of one bird (ID: 090122B), air mode was accidentally switched to normal mode while the bird was at the nest (presumably by the pecks of the bird), resulting in air mode on the first day and normal mode on the second day. Note that the bird stayed at the surface without diving between flights, which is suggestive of resting. The power requirement for flapping flight is high and is directly affected by air speed (Norberg, 1990; Pennycuick, 2008). 1). Second, the wings of cormorants are characterized by a low aspect ratio (7.6 in this study) and a short wingspan (1.2 m in this study) for their size among seabirds (Gaston, 2004). This is consistent with observations that Kerguelen shags prey on benthic animals, including nototheniid fishes (T. R. Cook, C.-A.B. Feathers have long been recognized as a classic example of efficient water-shedding — as in the well-known expression “like water off a duck’s back.” A combination of modeling and laboratory tests has now determined how both chemistry — the preening oil that birds use — and the microstructure of feathers, with their barbs and barbules, allow birds to stay dry even after emerging from amazingly deep dives. By contrast, it is advantageous for breath-hold diving, because oxygen storage capacity increases with size more rapidly than the rate of oxygen metabolism, enabling larger animals to dive deeper and longer (Halsey et al., 2006). Nevertheless, detailed behavioural and biomechanical analysis on the flight behaviour of seabirds in the context of the flight–diving compromise is still lacking. MB was estimated using the allometric equation specific to seabirds (Ellis and Gabrielsen, 2002): The work was supported by the Army Research Office, the Office of Naval Research, and the MIT-Legatum Center for Development and Entrepreneurship. But even after the collapse of the protective air layer, the preen oil changes the energy required to fully wet the feather’s barbs and barbules: In short, the wetting is reversible. dive depth, duration and swim speed) using miniaturized animal-attached tags are now well established (Ropert-Coudert and Wilson, 2005), those to record flight behaviour (e.g. These observations suggest that surfacing periods have a function of rest, and that longer flights require longer surfacing periods. This prediction can be tested by recording the flight air speed of seabirds in known ecological contexts (e.g. Pind is calculated as: “By putting our own coating on it, then we can look at just the structure. Helen Skaer, Mike O'Donnell and Julian Dow remember Simon in their affectionate Obituary. Sampling intervals were set at 1 s for depth, temperature and GPS positions, 1/32 or 1/64 s for accelerations, and 1, 1/4 or 1/8 s for speed.