Apus Apus Research Articles

Cool birds: first evidence of energy-saving nocturnal torpor in free-living common swifts Apus apus resting in their nests.

Daily torpor is a means of saving energy by controlled lowering of the metabolic rate (MR) during resting, usually coupled with a decrease in body temperature. We studied nocturnal daily torpor under natural conditions in free-living common swifts Apus apus resting in their nests as a family using two non-invasive approaches. First, we monitored nest temperature (Tnest) in up to 50 occupied nests per breeding season in 2010–2015. Drops in Tnest were the first indication of torpor. Among 16 673 observations, we detected 423 events of substantial drops in Tnest of on average 8.6°C. Second, we measured MR of the families inside nest-boxes prepared for calorimetric measurements during cold periods in the breeding seasons of 2017 and 2018. We measured oxygen consumption and carbon dioxide production using a mobile indirect respirometer and calculated the percentage reduction in MR. During six torpor events observed, MR was gradually reduced by on average 56% from the reference value followed by a decrease in Tnest of on average 7.6°C. By contrast, MR only decreased by about 33% on nights without torpor. Our field data gave an indication of daily torpor, which is used as a strategy for energy saving in free-living common swifts.

Species diversity of butterflies in Gaya district (Bihar)

Seventy-two species of butterflies belonging to five families was recorded for first time from Gaya district. Six sites were selected post pilot survey on the basis of both, nectar and larval host plant richness, diversity and anthropogenic pressure along with road connectivity. The maximum species diversity and richness was observed in winter season, while minimum in summer season. Plain tiger, Common jezebel, Common crow, Common castor, Tawny castor, Common emigrant, Peacock pansy, Grey pansy, Chocolate pansy, Common Pierrot, Lime blue, Great Eggfly, Common grass yellow, Common sailor, Common evening brown and Small branded swift were dominant butterfly species in all selected sites while Common Silverline, Indian sunbeam and Apefly were rare. Pollution due to dust, vehicular movements and activities like damaging nectar and larval host plant during breeding season, in and around habitat, due to lack of information seems to adversely effect the species diversity and population density in the region. Key words: - Butterfly, Species diversity, Gaya, Bihar.

On the wing

Birds are fascinating. For one thing, they can do what we cannot, like flying—as easily as anything at that, like a flock of Common Swifts Apus apus hastening through the late summer skies with their piercing screams, or a Wandering Albatross Diomedea exulans whose tip of the wing slices the ocean surface while the bird rides the wave troughs. For another, their appearance, their song, and their behaviours are so incredibly variable. In short, if you have ever really seen a bird, you will be forever smitten.

Effectiveness of using nest boxes as a form of bird protection after building modernization

Modernization of urban buildings can decrease the availability of nesting sites in buildings, leading to sudden decreases in the density of avifauna. In this study, we investigated the use of nest boxes as a bird conservation measure after buildings were thermally modernized. In a 10 ha experimental area we mounted five types of nest boxes of different sizes and dimensions (a total of 132). Nest boxes were dedicated to species that lost access to their previous nesting sites. All species associated with the buildings significantly declined or disappeared. In the first year after the modernization, the House Sparrow (Passer domesticus) decreased by 66% compared with the period before the modernization, Eurasian Jackdaw (Corvus monedula) by 68%, Common Starling (Sturnus vulgaris) by 70%, and Common Swift (Apus apus) by 100%. In the first two years after the modernization, the birds nested only in nest boxes. Five years of monitoring showed that using nest boxes as compensation for bird nesting sites lost during the renovation of buildings can cause a population to recover to ca. 50% of its original level. To optimize deployments of nest boxes, wildlife managers should consider target species’ preferences for the dimensions and placement of boxes and limit the time boxes are used if a species prefers nesting outside nest-boxes, but in buildings (e. g. the House Sparrow) and does not require additional support.

Reactions of breeding common swifts (Apus apus) to explosions

Sonic booms or disruptive explosions cause differing response in wildlife. In May 2021, when missiles were fired at urban areas in Israel, we observed the responses of breeding common swifts (Apus apus). In both nests, the initial boom resulted in a startled awakening of the swifts. In one case, a parent engaged in displacement behaviour of feeding the young while in the second case a parent tried to clamber up the walls. Our data support earlier studies that although auditory booms are disruptive, they do not result in nest abandonment or nest failure.

Examination of common swifts (Apus apus) for salmonella shedding in the area of Hannover, Lower Saxony, Germany.

The available literature indicates a high prevalence of the zoonotic pathogen Salmonella (S.) enterica serovar Infantis in the common swift (Apus apus). This long-distance migrant, which only consumes aerial plankton, can reach high population densities in places with suitable breeding sites. Dedicated competent private persons take part in the hand rearing of juvenile common swifts in wildlife rescue centres, which unavoidably results in close contact with these avian patients. For this reason, we examined common swifts for shedding of Salmonella spp. In the years 2014 and 2019, intestinal swabs or fresh faeces of common swifts (2014: n = 54; 2019: n = 62) were examined microbiologically (DIN EN ISO 6579; Annex D) in the area of Hannover, Lower Saxony, Germany. Salmonella spp. could not be detected in any of the examined common swifts within the investigation period and the studied area in 2014 and 2019. The results illustrate that the common swift is unlikely to be a natural reservoir of Salmonella spp. For the transmission of salmonella by swifts the local conditions with the corresponding environmental impact seem to play a significant role, and the risk of transmission should be assessed according to the region to be examined.

Onset of primary moult in immature and breeding adult Common Swifts Apus apus

ABSTRACT We studied the primary moult of immature and adult breeding Common Swift Apus apus in Italy. Birds were sampled at breeding colonies, or by attracting them to mist nets with the playback of recorded calls. Our sample of 590 immatures (2cy) assessed that about a quarter (25.6%) of these birds start moulting the inner primaries during their stay in Europe. We find that this moult starts usually in the second half of June, earlier than was observed in other European countries, where individuals begin moulting in July. Interestingly, and in contrast to previous knowledge on the moulting schedules of breeding Common Swifts, we found that more than half of breeding adults (56%, 15 of 27) started their primary moult in July. Moult before the swifts left our study area was limited to the first two inner primaries. Our study showed that breeding Commons Swifts are able to regulate their moult when already engaged in rearing young, and both immature and adult Swifts start their moult before leaving Europe towards their African winter quarters.

Wake characteristics of a freely rotating bioinspired swept rotor blade.

Rotor blades can be found in many engineering applications, mainly associated with converting energy from fluids to work (or electricity). Rotor blade geometry is a key factor in the mechanical efficiency of the energy conversion process. For example, wind turbines' performance directly depends on the blade geometry and the wake flow formed behind them. We suggest to use a bioinspired blade based on the common swift wing. Common swift (Apus apus) is known to be a long-distance flyer, able to stay aloft for long periods of time by maintaining high lift and low drag. We study the near-wake flow characteristics of a freely rotating rotor with swept blades and its aerodynamic loads. These are compared with a straight-bladed rotor. The experiments were conducted in a water flume using particle image velocimetry (PIV) technique. Both blades were studied for four different flow speeds with freestream Reynolds numbers ranging from 23 000 to 41 000. Our results show that the near wake developed behind the swept-back blade was significantly different from the straight blade configuration. The near wake developed behind the swept-back blade exhibited relatively lower momentum loss and suppressed turbulent activity (mixing and production) compared with the straight blade. Comparing the aerodynamic characteristics, though the swept-back blade generated relatively less lift than the straight blade, the drag was relatively low. Thus, the swept-back blade produced two to three times higher lift-to-drag ratio than the straight blade. Based on these observations, we suggest that, with improved design optimizations, using the swept-back configuration in rotor blades (specifically used in wind turbines) can improve mechanical efficiency and reduce the energy loss during the conversion process.

Wind-assisted sprint migration in northern swifts

SummaryLong-distance migration has evolved repeatedly in animals and covers substantial distances across the globe. The overall speed of migration in birds is determined by fueling rate at stopover, flight speed, power consumption during flight, and wind support. The highest speeds (500 km/day) have been predicted in small birds with a fly-and-forage strategy, such as swallows and swifts. Here, we use GLS tracking data for common swifts breeding in the northern part of the European range to study seasonal migration strategies and overall migration speeds. The data reveal estimated overall migration speeds substantially higher (average: 570 km/day; maximum: 832 km/day over 9 days) than predicted for swifts. In spring, swift routes provided 20% higher tailwind support than in autumn. Sustained migration speeds of this magnitude can only be achieved in small birds by a combined strategy including high fueling rate at stopover, fly-and-forage during migration, and selective use of tailwinds.

Monitoring of Organochlorine Pesticide and Polychlorinated Biphenyl Residues in Common Swifts (Apus apus) in the Region of Hannover, Lower Saxony, Germany.

The use of pesticides is associated with the decline of several avian species. In this study, we monitored the organochlorine contaminants in common swifts (Apus apus) in the years 2016 to 2018. These long-distance migrants breed in Europe and winter in Africa. Their only feeding source is aerial plankton. Pooled organ samples of 42 adult and 40 juvenile swifts were tested with the multi-residue method by gas chromatography-mass spectrometry (GC-TOF/MS). Predominantly, 4,4′-DDE, dieldrin, hexachlorobenzene (HCB), lindane and polychlorinated biphenyls (PCBs) were found in most of these common swifts. Only 4,4′-DDE (adult: 83 ± 70 μg/kg, juvenile: 17 ± 39 μg/kg) and dieldrin (adult: 2 ± 3 μg/kg, juvenile: 0.3 ± 1 μg/kg) concentrations were significantly different between adult and juvenile birds. All detected concentrations in our study were far lower than the previously recorded pesticide concentrations of common swifts in Italy and those which are known to cause toxicity and death in birds.

First record of Forbes-Watson's Swift Apus berliozi in southern Africa, with comments on vocal and visual identification

We report the first record of Forbes-Watson's Swift Apus berliozi for the southern Africa region from coastal southern Mozambique. Identification was primarily based on vocal characters using sonogram analyses, which show that voice is diagnostic compared to all seven possible confusion species in the region. Current knowledge of the distribution and life history of A. berliozi is summarised, which shows that the Mozambique record extends the non-breeding range c.1,700 km south and suggests that Forbes-Watson's Swift is a migrant to the littoral of Tanzania and northern and central Mozambique. Field identification of Forbes-Watson's Swift using visual characters is challenging, but information is presented to aid separation from the most likely confusion species, Common Swift A. apus.

Design and kinematic analysis of flapping wing mechanism for common swift inspired micro aerial vehicle

The article presents a novel flapping wing mechanism for Micro Aerial Vehicle (MAV) inspired by one of the most efficient flyers of the aerial world, the Common swift ( Apus apus). The flight characteristics such as wing beat frequency, wing beat amplitude, and fore and aft movements, as well as wing rotation of the bird at a flight speed 8 m /s, were studied. The common swift rotates its hand wing keeping the pitch of the arm wing constant during the entire wingbeat cycle. The hand wing undergoes forward rotation during the downstroke and backward rotation during the upstroke. This complex wing kinematics enables swift to generate various unsteady aerodynamic mechanisms. Using the geometric and kinematic details, a flapping wing mechanism that emulates the wing kinematics of the bird was designed. The flapping wing mechanism based on the epicyclic ellipsograph mechanism presented herein integrates flapping motion, fore and aft motion, and selective wing rotation. Importantly, this fully constrained mechanism allows performing all the key kinematic motions of the common swift with a single actuator. A kinematic model of the mechanism is presented to calculate the design parameters based on the scale of the MAV. Kinematic simulation of the mechanism is also presented to verify the design.

Induced alloparental care in Common Swifts (Apus apus)

The Common Swift, in spite of being considered to be of Least Concern, is declining in many areas of its breeding range. In several countries nest-box programs have been initiated to counter these declines. In most cases, when nestlings fall out of their nests, they are taken to rehabilitation centres. Raising and caring for Common Swift nestlings is not easy, cheap and usually results in low survival rates. We experimented with introducing the rescued young into existing nests and found that they were readily accepted and all five of the young fledged successfully. We recommend alloparenting as the preferred option when precocial nestlings are rescued and active nests of other pairs are available.

Evolution of chain migration in an aerial insectivorous bird, the common swift Apus apus.

Spectacular long‐distance migration has evolved repeatedly in animals enabling exploration of resources separated in time and space. In birds, these patterns are largely driven by seasonality, cost of migration, and asymmetries in competition leading most often to leapfrog migration, where northern breeding populations winter furthest to the south. Here, we show that the highly aerial common swift Apus apus, spending the nonbreeding period on the wing, instead exhibits a rarely found chain migration pattern, where the most southern breeding populations in Europe migrate to wintering areas furthest to the south in Africa, whereas the northern populations winter to the north. The swifts concentrated in three major areas in sub‐Saharan Africa during the nonbreeding period, with substantial overlap of nearby breeding populations. We found that the southern breeding swifts were larger, raised more young, and arrived to the wintering areas with higher seasonal variation in greenness (Normalized Difference Vegetation Index) earlier than the northern breeding swifts. This unusual chain migration pattern in common swifts is largely driven by differential annual timing and we suggest it evolves by prior occupancy and dominance by size in the breeding quarters and by prior occupancy combined with diffuse competition in the winter.

Climate anomalies affect annual survival rates of swifts wintering in sub-Saharan Africa.

Several species of migratory swifts breed in the Western Palearctic, but they differ in reproductive traits and nonbreeding areas explored in Africa. We examined survival and recapture probabilities of two species of swifts by capture–mark–recapture data collected in northern Italy (Pallid Swift Apus pallidus in Carmagnola, Turin, and Common Swift Apus apus in Guiglia, Modena) in the breeding season (May–July). Apparent survival rates were relatively high (>71%), comparable to other studies of European swifts, but showed marked annual variations. We used geolocators to establish the exact wintering areas of birds breeding in our study colonies. Common Swifts explored the Sahel zone during migration and spent the winter in SE Africa, while the Pallid Swifts remained in the Sahel zone for a longer time, shifting locations southeast down to Cameroun and Nigeria later in winter. These movements followed the seasonal rains from north to south (October to December). In both species, we found large yearly differences in survival probabilities related to different climatic indices. In the Pallid Swift, wintering in Western Africa, the Sahel rainfall index best explained survival, with driest seasons associated with reduced survival. In the Common Swift, wintering in SE Africa, the El Niño–Southern Oscillation (ENSO) cycle performed significantly better than Sahel rainfall or North Atlantic Oscillation (NAO). Extreme events and precipitation anomalies in Eastern Africa during La Niña events resulted in reduced survival probabilities in Common Swifts. Our study shows that the two species of swifts have similar average annual survival, but their survival varies between years and is strongly affected by different climatic drivers associated with their respective wintering areas. This finding could suggest important ecological diversification that should be taken into account when comparing survival and area use of similar species that migrate between temperate breeding areas and tropical wintering areas.

Common Swifts (Apus apus) nesting in mature pine forests in Corsica

Tree breeding in holes has been recorded for the Common Swift (Apus apus) mainly in Northern Europe and Siberia. This behaviour, considered as ancestral, has also been noted in Corsican forests. Although marginal in terms of numbers, it is a perennial phenomenon. We present here a synthesis on the distribution and the characteristics of nesting sites, and we compare these breeding sites to the occurrences in continental Europe and Northern Africa. Our data add to the body of arguments in favour of the preservation of mature forests of the Corsican Pine on the island.

Light data from geolocation reveal patterns of nest visit frequency and suitable conditions for efficient nest site monitoring in Common Swifts Apus apus

ABSTRACTCapsule: We developed a protocol for efficient monitoring of potential Common Swift Apus apus nest sites which considers variation in nest visit frequency across the breeding season and in relation to time of day and weather.Aims: To investigate patterns of nest visit frequency in Common Swifts in order to improve the efficiency and reliability of the monitoring of nest sites threatened by building renovations.Methods: We derived information on nest attendance from light data recorded by geolocators from ten adult Common Swifts during three breeding seasons (n = 686 individual sampling days) and analysed how nest visit frequency varied across the breeding season and in relation to time of day and weather.Results: The mean nest visit frequency was 5.63 visits per bird per day (0.32 visits per hour of daylight). The daily number of visits was highest at the beginning of July during chick-rearing. Moreover, it was positively correlated with temperature and negatively correlated with rainfall and wind speed. Nest visit frequency showed a distinct peak around sunset, while also being relatively high in the morning and around noon.Conclusion: We recommend monitoring potential Common Swift nest sites in Central Europe between the end of June and mid-July during good weather between 0.50 and 7.75 h after sunrise or between 3.00 h before sunset and sunset, when observation bouts of 0.5–2.0 h provide an encounter probability greater than 90%. Our study shows that repurposing geolocator light data – usually used to study bird migration – for investigating nest attendance in cavity-breeding birds can provide important information for bird conservation.

Artificial Light at Night Promotes Activity Throughout the Night in Nesting Common Swifts (Apus apus)

The use of artificial light at night (ALAN) is a rapidly expanding anthropogenic effect that transforms nightscapes throughout the world, causing light pollution that affects ecosystems in a myriad of ways. One of these is changing or shifting activity rhythms, largely synchronized by light cues. We used acoustic loggers to record and quantify activity patterns during the night of a diurnal bird – the common swift – in a nesting colony exposed to extremely intensive artificial illumination throughout the night at Jerusalem’s Western Wall. We compared that to activity patterns at three other colonies exposed to none, medium, or medium-high ALAN. We found that in the lower-intensity ALAN colonies swifts ceased activity around sunset, later the more intense the lighting. At the Western Wall, however, swifts remained active throughout the night. This may have important implications for the birds’ physiology, breeding cycle, and fitness, and may have cascading effects on their ecosystems.

Leading-edge vortices over swept-back wings with varying sweep geometries.

Micro air vehicles are used in a myriad of applications, such as transportation and surveying. Their performance can be improved through the study of wing designs and lift generation techniques including leading-edge vortices (LEVs). Observation of natural fliers, e.g. birds and bats, has shown that LEVs are a major contributor to lift during flapping flight, and the common swift (Apus apus) has been observed to generate LEVs during gliding flight. We hypothesize that nonlinear swept-back wings generate a vortex in the leading-edge region, which can augment the lift in a similar manner to linear swept-back wings (i.e. delta wing) during gliding flight. Particle image velocimetry experiments were performed in a water flume to compare flow over two wing geometries: one with a nonlinear sweep (swift-like wing) and one with a linear sweep (delta wing). Experiments were performed at three spanwise planes and three angles of attack at a chord-based Reynolds number of 26 000. Streamlines, vorticity, swirling strength, and Q-criterion were used to identify LEVs. The results show similar LEV characteristics for delta and swift-like wing geometries. These similarities suggest that sweep geometries other than a linear sweep (i.e. delta wing) are capable of creating LEVs during gliding flight.

Flight activity in pallid swiftsApus pallidusduring the non‐breeding period

Flight activity recorders have recently confirmed that alpine and common swifts spend the majority of their non‐breeding period on the wing, which may last 6–10 months. Here we test the hypothesis that the closely related pallid swift, a species with a breeding distribution around the Mediterranean, lead a similar aerial life‐style during its migration and wintering periods. The pallid swift usually lays two clutches in one season and therefore spends more time in the breeding area than the common swift. We successfully tracked four pallid swifts with data loggers that record light for geolocation and acceleration every 5 min to monitor flight activity. The birds wintered south of the Sahel in west Africa from the Ivory Coast to Cameroon. The pallid swifts spent the majority of their non‐breeding time in flight, especially the first two months after leaving the breeding area in autumn, while a few landing events occurred during the winter. The total time grounded was < 1%, similar to that of the common and alpine swifts. The mass specific flight metabolic rate of swifts is similar to the average non‐breeding metabolic rate of a long distance terrestrial migrant, suggesting swifts are not more likely to procure oxidative damage as a consequence of continuous flight than other migrants. The open airspace used by swifts may provide a relatively safe habitat that explain the high survival rate found in swifts.