Effects of geolocators on reproductive performance and annual return rates of a migratory songbird

Our understanding of the annual life-cycle movements of small migratory birds has advanced rapidly with the advent of light-weight geographical positioning devices (i.e., geolocators), yet the effects of geolocators on reproduction and survival have not been adequately quantified. We tested for impacts of attaching a 1-g geolocator (using a harness around the legs and back, anterior to the tail) to adult Tree Swallows (Tachycineta bicolor) on parental feeding behavior, nestling growth and size, fledging success, and return rates between 2011 and 2012. At one breeding site, we compared feeding visits, nestling growth, and nestling size between paired nest boxes where one parent was marked at the 'geolocator' box with a 'control' nest box where neither parent was marked. We detected no differences between geolocator and control nests in either the frequency of feeding visits to nestlings or the amount of time spent at nests. Birds marked with geolocators fed nestlings as frequently as their unmarked mates. Likewise, nestlings raised at geolocator nests grew at similar rates to those at control nests, and had similar structural size and body mass at fledging. At three widely-separated sites across the Tree Swallow breeding range in Canada, we also found that fledging success was similar for geolocator and control nests. Although we found no evidence for short-term negative impacts of geolocators, the return rates of geolocator-marked Tree Swallows tended to be significantly lower than those of unmarked control birds. Thus, we found little evidence for short-term impacts of geolocators on reproduction but our study does suggest that long-term impacts of geolocators could be manifested in terms of lower survival, higher emigration rates, or lower breeding propensity. © 2013 Dt. Ornithologen-Gesellschaft e.V.Peer Reviewe

Cross-hemisphere migration of a 25 g songbird

The northern wheatear (Oenanthe oenanthe) is a small (approx. 25 g), insectivorous migrant with one of the largest ranges of any songbird in the world, breeding from the eastern Canadian Arctic across Greenland, Eurasia and into Alaska (AK). However, there is no evidence that breeding populations in the New World have established overwintering sites in the Western Hemisphere. Using light-level geolocators, we demonstrate that individuals from these New World regions overwinter in northern sub-Sahara Africa, with Alaskan birds travelling approximately 14 500 km each way and an eastern Canadian Arctic bird crossing a wide stretch of the North Atlantic (approx. 3500 km). These remarkable journeys, particularly for a bird of this size, last between one to three months depending on breeding location and season (autumn/spring) and result in mean overall migration speeds of up to 290 km d−1. Stable-hydrogen isotope analysis of winter-grown feathers sampled from breeding birds generally support the notion that Alaskan birds overwinter primarily in eastern Africa and eastern Canadian Arctic birds overwinter mainly in western Africa. Our results provide the first evidence of a migratory songbird capable of linking African ecosystems of the Old World with Arctic regions of the New World

Metals and metal isotopes incorporation in insect wings: Implications for geolocation and pollution exposure

Anthropogenic activities are exposing insects to elevated levels of toxic metals and are altering the bioavailability of essential metals. Metals and metal isotopes have also become promising tools for the geolocation of migratory insects. Understanding the pathways of metal incorporation in insect tissues is thus important for assessing the role of metals in insect physiology and ecology and for the development of metals and metal isotopes as geolocation tools. We conducted a diet-switching experiment on monarch butterflies [Danaus plexippus (L.)] with controlled larval and adult diets to evaluate the sources of 23 metals and metalloids, strontium isotopes, and lead isotopes to insect wing tissues over a period of 8 weeks. Concentrations of Ca, Co, Mo, and Sb differed between the sexes or with body mass. Ni and Zn bioaccumulated in the insect wing tissues over time, likely from the adult diet, while increases in Al, Cr, Cd, Cu, Fe, and Pb were, at least partially, from external sources (i.e., dust aerosols). Bioaccumulation of Pb in the monarch wings was confirmed by Pb isotopes to mainly be sourced from external anthropogenic sources, revealing the potential of Pb isotopes to become an indicator and tracer of metal pollution exposure along migratory paths. Concentrations of Ba, Cs, Mg, Na, Rb, Sr, Ti, Tl, and U appeared to be unaffected by intrinsic factors or additions of metals from adult dietary or external sources, and their potential for geolocation should be further explored. Strontium isotope ratios remained indicative of the larval diet, at least in males, supporting its potential as a geolocation tool. However, the difference in strontium isotope ratios between sexes, as well as the possibility of external contamination by wetting, requires further investigation. Our results demonstrate the complexity of metal incorporation processes in insects and the value of studying metals to develop new tools to quantify pollution exposure, metal toxicity, micronutrient uptake, and insect mobility.This study was funded by the New Frontiers in Research Fund (CB and GT) and Syngenta Canada, Inc. (RN). GT acknowledges funding from the grant PID2020-117739GA-I00 from MCIN/AEI/10.13039/501100011033 and the grant LINKA20399 from the CSIC iLink program. MR was supported by the Queen Elizabeth II Graduate Scholarship in Science and Technology (QEII-GSST) and an OntarioGraduate Scholarship.1. Introduction 2. Materials and methods 2.1. Diet-switching experiment 2.1.1. Trace element analysis 2.1.2. Strontium isotope ratios analysis 2.1.3. Lead isotope ratios analysis 2.1.4. Statistical analysis 2.1.5. Mobility index and enrichment factors 2.2. Wetting experiment 2.3. Natural metal concentrations in monarchs 3. Results 3.1. Metals classified into four categories 3.2. Strontium and strontium isotope ratios 3.3. Lead and lead isotope ratios 3.4. Natural metal concentrations in lab-raised and wild monarchs 4. Discussion 4.1. Regulation of metals in insect wings 4.2. Bioaccumulation of metals in insect wings 4.3. Geolocation using metals and metal isotopes 4.4. Natural metal concentrations 5. Conclusion Data availability statement Author contributions Funding Acknowledgments Conflict of interest Publisher’s note Supplementary material Reference