Coppack T.,Institute of Applied Ecology IfAO |
Bairlein F.,Institute of Avian Research Vogelwarte Helgoland
Journal of Ornithology | Year: 2011
Bird migration has evolved under the influence of annual and daily fluctuations in resource availability. Numerous passerine migrants migrate exclusively by night, maximizing the time available for foraging and feeding during the day. When held in captivity, and in total absence of environmental cues, nocturnal migrants typically show rhythms of night-time restlessness (Zugunruhe), which persist with a periodicity of about 24 h. Experimental evidence suggests that these circadian rhythms of Zugunruhe may either result from a "redefinition" of the diurnal clock or from changes in the phase relationship between independent endogenous oscillators. The role of melatonin in this control system remains ambiguous. Lowered levels of circulating melatonin found during migratory nights could either be the positive stimulus, a permissive factor or a side effect of nocturnal wakefulness. Although the nutritional state of a migrant is known to strongly influence the incidence of migratory activity, the physiological link between the circadian clock controlling Zugunruhe and the metabolic/hormonal path-ways that regulate the incidence of migration is uncertain. A functional genetic approach promises to bring behavioural and physiological knowledge together. Determining the mechanisms that are involved in the day-to-day scheduling of migration is crucial for understanding the overall control of migration, as the sum of migratory nights determines for how long, and how far, a migrant potentially travels. © Dt. Ornithologen-Gesellschaft e.V. 2011.
Kalbe J.,University of Potsdam |
Kalbe J.,Institute of Applied Ecology IfAO |
Jagher R.,University of Basel |
Pumpin C.,University of Basel
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2016
The site Nadaouiyeh Aïn Askar, an ancient artesian spring near the village of El Kowm, Central Syria, is an example of long lasting human occupation in a desert environment throughout the Middle and Late Pleistocene. The excavations expose a succession of sedimentary units, containing an artifact assemblage assigned to the Acheulean techno-complex. Unit VI, attributed to the Marine Isotope Stage 13, is rich in ostracod valves and was chosen for the present environmental study. From these sediments Heterocypris salina, H. incongruens, Cyprideis torosa, Ilyocypris cf. bradyi, I. inermis, I. cf. gibba, Darwinula stevensoni, Plesiocypridopsis newtoni, Pseudocandona compressa, Candona cf. neglecta, Pseudocandona sp., Trajancypris sp., Physocypria sp. and Mixtacandona sp. are documented for the first time in the Middle Pleistocene of the arid environment of central Syria. Data from these microfossils as well as geochemical proxies implicate three phases, turning the wetland from a palustrine setting into a spring supplied pond with increasing salinity. The high mineralization of the spring waters enables a discussion about early hominin adaptability to brackish waters as drinking water resources, common within the steppe and desert environments along the "out-of-Africa"-corridor in the eastern Mediterranean. © 2016 Elsevier B.V.
Lin T.,Chinese Institute of Urban Environment |
Lin T.,Xiamen Key Laboratory of Urban Metabolism |
Coppack T.,Institute of Applied Ecology IfAO |
Lin Q.-X.,Xiamen University |
And 6 more authors.
Ecological Indicators | Year: 2012
Urbanization is dramatically altering biodiversity and ecosystem health worldwide. Birds are highly reactive to environmental change and are thus important indicators of ecological condition at both a global and a local scale. Flight initiation distance (FID) is generally used as a quantitative measure of a bird's tolerance to human-caused disturbance and may indicate how well a species or population has become adapted to chronic environmental stress. Here, we address the following questions, looking at species-specific FID values in different habitats along the urban-rural gradient: (a) Are within-species FID values generally lower in strongly urbanized areas than in more rural areas? And if so, (b) does variation of FID (VFID) indicate species-specific tolerance to urbanization? From 2008 to 2009, we measured FID in coastal bird species at eight sites along the urbanized coast of Xiamen, China, in a total of 254 trials. The results indicate that bird species with a high propensity to disperse and with large population sizes tend to decrease their FID more strongly along the urban-rural habitat gradient. This pattern was most apparent in the Little Egret (Egretta garzetta). Based on VFID, 17 bird species out of 36 were classified as being tolerant to urban environmental conditions, with FID values showing decreasing trends along the urban-rural gradient, as in the Little Egret. Our results suggest that VFID may be the relevant measure for analyzing birds' tolerance to urbanization and for assessing the speed by which species or populations can adjust or adapt to novel environmental conditions. © 2011 Elsevier Ltd. All rights reserved.
Sjoberg S.,Lund University |
Alerstam T.,Lund University |
Akesson S.,Lund University |
Schulz A.,Institute of Applied Ecology IfAO |
And 3 more authors.
Animal Behaviour | Year: 2015
Departure decisions of how and when to leave a stopover site may be of critical importance for the migration performance of birds. We used an automated radiotelemetry system at Falsterbo peninsula, Sweden, to study stopover behaviour and route choice in free-flying passerines departing on flights across the Baltic Sea during autumn migration. In addition, we had an offshore receiver station (FINO 2) located about 50. km southeast from Falsterbo. Of 91 birds equipped with radiotransmitters, 19 passed FINO 2. The probability that a departing migrant passed near FINO 2 was primarily affected by winds and timing of departure. Probably, the migrants were subjected to drift by westerly winds, leading to southeasterly flight paths and an enhanced probability of passing FINO 2. Most birds passing the offshore station departed early in the night, which indicates that southward departures across the Baltic Sea usually take place during this time window. Wind condition was the dominant factor explaining the variation in flight duration between Falsterbo and FINO 2. After considering wind influence, we found additional effects of fat score and cloud cover. Birds with a higher fat score performed the flight faster than leaner individuals, as did birds that departed under clear skies compared to birds departing during overcast skies. These effects may reflect a difference in migratory motivation and airspeed between lean and fat birds together with difficulties in controlling orientation in overcast situations on oversea flights when celestial cues are unavailable. Thus, winds, clouds and fuel reserves were the primary factors determining departure and flight decisions in passerine migrants at Falsterbo in autumn. © 2015 The Association for the Study of Animal Behaviour.