Parent-offspring and inter-offspring responses to conspecific vs heterospecific distress calls in two sympatric birds

Distress calls, as a type of alarm call, play important roles in expressing bodily condition and conveying information concerning predation threats. In this study, we examined the communication via distress calls in parent–offspring and inter-offspring interactions. First, we used playback of chick distress calls of two sympatric breeders, the vinous-throated parrotbill Sinosuthora webbiana and the oriental reed warbler Acrocephalus orientalis, to the adults/chicks of these two species respectively and measured the responses of conspecifics or heterospecifics. The playback-to-chicks experiment showed that both species of chicks reduced the number of begging calls and begging duration time as a response to conspecific/heterospecific distress calls compared with natural begging and background noise controls. However, reed warbler chicks also reduced beak opening frequency in the response to conspecific distress calls compared with other playback stimuli. Second, the results of the playback-to-adults experiment showed that reed warbler adults could eavesdrop on distress calls of conspecific neighbors and sympatric heterospecifics. Furthermore, the nest-leaving behavior of reed warblers did not differ significantly when they heard the distress calls of conspecifics or parrotbills. Finally, reed warbler adults responded to conspecific distress calls more quickly than to heterospecific distress calls, while parrotbill adults presented the opposite response. Our results supported the warn-kin hypothesis and show that chick distress calls play an important role in conveying risk and the condition of chicks to enhance individual fitness. In addition, we also found that eavesdropping on distress calls is a congenital behavior that begins in the chick stage.

Sound attenuation in the ear of domestic chickens ( Gallus gallus domesticus ) as a result of beak opening

Because the quadrate and the eardrum are connected, the hypothesis was tested that birds attenuate the transmission of sound through their ears by opening the bill, which potentially serves as an additional protective mechanism for self-generated vocalizations. In domestic chickens, it was examined if a difference exists between hens and roosters, given the difference in vocalization capacity between the sexes. To test the hypothesis, vibrations of the columellar footplate were measured ex vivo with laser Doppler vibrometry (LDV) for closed and maximally opened beak conditions, with sounds introduced at the ear canal. The average attenuation was 3.5 dB in roosters and only 0.5 dB in hens. To demonstrate the importance of a putative protective mechanism, audio recordings were performed of a crowing rooster. Sound pressures levels of 133.5 dB were recorded near the ears. The frequency content of the vocalizations was in accordance with the range of highest hearing sensitivity in chickens. The results indicate a small but significant difference in sound attenuation between hens and roosters. However, the amount of attenuation as measured in the experiments on both hens and roosters is small and will provide little effective protection in addition to other mechanisms such as stapedius muscle activity.

Behavioural responses, traumatic injuries and live weight losses in ostrich (<i>Struthio camelus</i>) chicks transported by road during hot-dry conditions

The aim of this study was to evaluate the effect of six-hour road transportation on behavioural activities, live weight and traumatic injuries of 40 (20 males and 20 females) ostrich chicks age 3.5 months. The average weight of the birds was 27.7 kg. Four separate journeys were conducted and each vehicle was loaded with 10 ostriches. The behavioural events, environmental data, live weights and traumatic injuries were recorded before, during and after transportation. The result showed that the most stressful behaviours exhibited by the chicks during transportation were hyperventilation (66.7±21.2 %), wing fluffing (65±12.0 %), and prolonged standing (60±15.3 %). The most frequent behaviours per hour of the journey were beak opening (5.9±1.8 bouts), elimination (5.3±2.3 bouts) and pecking (5.6±2.8 bouts). The chicks spent 27.0±11.8, 18.2±1.0, and 17.5±0.1 min per hour of the journey, standing, restless and lying down, respectively. 15.0±2.3 % of the chicks sustained mild injuries during handling and loading. The birds lost 6.5±1.4 % of their live weight after transportation. The relationships between the journey period, temperature humidity index (THI) and stressful behaviours of wing fluffing, pecking, hyperventilation (beak opening) and lying down recorded during the transportation was positive and significant (P<0.01), while behaviours of standing, elimination and restlessness were negatively and significantly (P<0.01) correlated. Student's t-test and Pearson’s correlation test were employed in the statistical analysis. The results suggest that THI of 33–40 °C constitutes moderate risk, while that of 47 °C and above may result in severe stressful behaviours, and this may be considered as recommended ranges and limits of thermal load values in transported chicks. In conclusion, six hours road transportation during hot-dry conditions and the introduction of ostrich chicks into a new environment post-transportation induce behavioural stress.

Short Underwater Opening of the Beak Following Immersion in Seven Penguin Species

Videocamera recordings of seven species of penguin, Emperor (Aptenodytes forsteri), Humboldt (Spheniscus humboldti), Adélie (Pygoscelis adeliae), Chinstrap (P. antarctica), Gentoo (P. papua), Macaroni (Eudyptes chrysolophus) and Rockhopper (E. chrysocome), swimming in large aquaria revealed that birds opened their beak underwater for less than a second immediately after initiating a dive. Overall, this beak-opening occurred in 64% of the immersions but, in all species, was associated with quick transitions between air and water, such as in porpoising or dives that were initiated rapidly. Two hypotheses are proposed to explain this behavior: beak-opening may be a signal that initiates bradycardia, such as is observed in unrestrained diving animals, or beak-opening may be associated with chemoreception to help detect potential prey or predators. Breve Apertura del Pico en Pingüinos luego de Sumergirse Resumen. En acuarios registramos con cámara de video a siete especies de pingüinos, Aptenodytes forsteri, Spheniscus humboldti, Pygoscelis adeliae, P. antarctica, P. papua, Eudyptes chrysolophus y E. chrysocome. Los registros indicaron que las aves abren el pico bajo el agua por menos de un segundo inmediatamente después de sumergirse al iniciar el buceo. En total, esta apertura del pico se registró en el 64% de las inmersiones y en todas las especies ocurrió preferentemente en situaciones de transición rápida entre aire y agua, como en “porpoising” o en buceos que se iniciaron abruptamente. Se proponen dos hipótesis para explicar esta conducta: la apertura del pico puede servir como una señal para iniciar la bradicardia, como se observa en animales buceando voluntariamente, o bien la apertura del pico podría estar asociada a quimiorecepción para detectar potenciales presas o depredadores.

THE COOLING POWER OF THE PIGEON HEAD

Resting pigeons preheated to a stable core temperature of 43.2 &deg;C, which is within the range of body temperatures recorded during flight, were able to cool their body at high rates if their head and upper neck were exposed to an air stream at 23.5 &deg;C. The heat dissipation capacity of the head and neck, estimated from measurements made at a wind speed (100 km h-1) corresponding to fast flight, was 9.8 W, or 4.5 times the resting heat production. Since the greater part of this capacity, about 8 W, was attributable to the inner surfaces of the mouth, ram ventilation of the buccal cavity appears to be an important mechanism for increasing evaporative heat loss during flight. Accordingly, wind-assisted mouth cooling should be utilized by resting pigeons, since exposure to a slight breeze (approximately 10 km h-1) could augment their dissipating power by an amount equivalent to their resting metabolic rate. It is concluded that beak opening, together with a source of convection other than panting and gular flutter, is required to exploit fully the heat dissipation capacity of the buccopharyngeal mucosa of birds.

Pecking of the Pigeon (Columba Livia L.)

Abstract1. The pecking behaviour of pigeons is described from a frame-by-frame analysis of high speed films and X-ray motion pictures. 2. Each pecking scene has four discrete steps. These steps run from the fixation of the head above the seed to (1) the grasp of the seed by the beak tips to (2) the catching of the seed at the rictus level to (3) the positioning of the seed along the caudal palate to (4) its arrival in the rostral oesophagus. The bird is able to stop the sequence at the very beginning of each step. For example by a refusal to continue after the final fixation, by dropping the seed after the grasp, by ejecting it after the rictus catch when the seed is positioned on the lingual base, and probably also by an ejection following the positioning along the caudal palate. If necessary, an adjustment of the system takes place, prior to each step. Such an adjustment positions the structural elements and/or the seed in the correct mechanical arrangement for the initiation of the next step in the sequence. These adjustments are the preliminary approach at the final fixation, stationing at the grasp, repetition of transport through the mouth to the rictus level, and repetition of the transport type used in the pharynx. The bird has the possibility to adapt each step to either the position and/or the size of the seed. The final approach (step 1) can be a scooping, a straight or a swinging approach of the head depending upon the seed's position, while simultaneously the type of beak opening is adapted to the seed's position and the gape size to the seed's size. Transport through the mouth (step 2) is for a small seed a slide-and-glue mechanism by which the seed is adhered to the tongue and is carried to the rictus level. Usually large seeds are transported by the catch-and-throw mechanism. Intermediate types also occur. For small seeds transport to the caudal palate (step 3) is also a slide-and-glue mechanism, in which the lingual base serves as the adhering element. When large seeds are transported a head jerk is added to this mechanism. Transport into the oesophagus (step 4) for small seeds is a scraping mechanism of the ventral pharyngeal valves which are erected when they are in front of the seed prior to their retraction. An extra laryngeal transporting cycle and head jerk occur when large seeds are swallowed. 3. The slide-and-glue mechanism is extended by prediction of position and structure of glands deduced from the mechanical requirements of the mechanism. After comparison of the deduced glands with a microscopic and scanning electron microscopic analysis of the mouth and pharynx, the position and the structure of the gl. mandibularis anterior, the gl. mandibularis posterior, the gl. lingualis superior, the gl. lingualis inferior and the gl. palatina posterior externa were found to correspond with the prediction. 4. The existence of a cerebral comparator-selector mechanism was assumed to describe decision making processes during the adjustment of the pecking system at the start of each step. This is most clearly shown during stationing, which is a repositioning of the seed after the grasp. The registered position of the seed is compared with a pre-set cerebral template and after the comparison a selector recruits either mechanical units for a positive output (a head jerk and a gape cycle) transporting the seed somewhat caudad, or a negative output (a gape cycle and a lingual cycle) transporting the seed rostrad. 5. The close relationship between the particular positioning of the sensory units and the necessarily coupled recruitment of a set of mechanical units is analysed. For example, during final fixation the visual information must be gathered for the complete composition of the final appraoch. 6. From the stereotyped appearance of parts of the pecking behaviour it is shown that pecking better viewed as a variable sequence of fixed action patterns rather than just one such a pattern, by handling coupling of mechanical units as a constraint resulting from mechanical construction, mechanical operation, positioning of sense organs, availability of neuronal circuits and necessity to learn optimal combination of available mechanical units. Further, it is shown that the shift of the pigeon's food preference to larger sized seeds after trigeminal deafferentation can be explained as a preference for a catch-and-throw mechanism. Finally, it is shown that a partial refinement of an optimal foraging strategy is found even at the lower levels of organization of pecking.