Past Research at the ASCC



Nathalie Bays

François Bolduc

Jovette Bouchard


Andrew Boyne

Joanna Coleman

Kim Fernie

Alain Fontaine and Marc Pauzé


Oliver P. Love

Annie Tremblay


 

 

 


 

The effects of Herring Gulls (Larus argentatus) on the vegetation and soils of their nesting sites

    This study was initiated to determine the effects of Herring Gulls (Larus argentatus) on the vegetation and soils of their nesting sites within the Mingan Island National Park Reserve. Both vegetation (species composition, cover, density, growth) and soil characteristics (pH, N, P, K, Ca, Mg) were monitored throughout the 1995 breeding season. Exclosures were installed within the colonies as control sites to prevent gull activity and these were compared to “treatment plots” or areas where gulls were present. All plants located at the study sites were native perennials with the exception of Stellaria, a native annual. Ledum groenlandicum was the only plant species significantly affected by gull activities. Both % cover and shoot growth for Ledum were greater in the exclosures than in the treatment plots over the breeding season. The gulls were also found to significantly increase pH and phosphorous levels in the soil through the deposition of faeces. Gull roosting sites were found to have higher nutrient levels than the nesting areas (treatment plots). The gulls appear to have some effect, as this short term study suggests, however it is imperative the exclosures remain in place to monitor for any long term changes which may occur.

Les effets du goéland argenté (Larus argentatus) sur la végétation et le sol aux sites de nidification

Cette étude avait pour but de déterminer l'effet des goélands argentés (Larus argentatus) sur la végétation et les sols aux alentours de leurs sites de nidification à la Résèrve du Parc National de l’archipel de Mingan. La végétation (espèces, couverture, densité, croissance) ainsi que les nutriments du sol (pH, N, P, K, Ca, Mg) ont été suivis pendant la saison de reproduction 1995 dans des traitements (avec goélands) et des exclos contrôles excluant  toute activité de reproduction des goélands argentés. Les éspèces végétales retrouvées dans les sites étaient toutes spontanées et vivaces avec l'exception de Stellaria, une plante annuelle. Ledum groenlandicum est la seul éspèce qui a été affectée par les goélands et dont le pourcentage de recouvrement et la croissance a été significativement (P < 0.10) plus elevés dans les exclos-contrôles que dans les traitements. Les goélands ont également eu un effet sur les sols en augmentant significativement (P<0.10) le pH ainsi que le taux de phosphore. Les lieux de repos des goélands avaient des niveaux de nutriments plus élevés que les périmetres (sites de nidification). Les goélands ont eu peut d’effet significatif à cour terme mais il est impératif que les exclos restent en place pour surveiller les changements possibles à long terme.

Nathalie Bays
Back to Top

The impact of human disturbance on the nesting success of the Common Eider (Somateria mollissima)

The influence of human disturbance on the nesting success of the Common Eider (Somateria mollissima) was investigated in the Mingan Archipelago National Park Reserve during summers of 1994 to 1996.  Six colonies were used, four located on open islets and two on forested islands.  Three experimental treatments were used that entailed varying the frequency and time occurrence of visits in incubation.  Every year, each treatment was applied to several eider colonies differing in the density of nesting gulls on the same island.  During visits, incubating females were flushed and nest fate recorded.  Several variables were also measured during visits describing female quality (assessed by clutch size and laying date) and nest quality (assessed by nest concealment, distance to shore, vegetation height, and density of nesting gulls on the island).  Results showed that frequency of visits did not affect nesting success of eiders, mainly because most observed nest failures occurred after the first visit.  The time occurrence of the first visit during incubation was of primary importance; eider nests visited early were much more affected by our presence. The nesting success of eiders was related to the density of associated colonies of nesting gulls only when visits occurred during early incubation.  Female eiders of greater reproductive quality were the most successful when disturbed regularly.  These females were in greater proportion on islands associated with lower density of nesting gulls, i.e. on forested islands rather than on open islets.  Within colonies, they were mainly found nesting near shore where nest concealment is sparse.  Results showed that visits to eider colonies can greatly affect their reproductive output.  Visits during early incubation on open islets had the greatest impact.

L'impact des perturbations humaines sur le succès de nidification de l'Eider à Duvet (Somateria mollissima)

L’influence de visites à des colonies d’eiders à duvet (Somateria mollissima)  sur leur succès de nidification a été évalué à l’intérieur de la Réserve Nationale de Parc de l’Archipel de Mingan. Pour se faire, nous avons suivi de 1994 à 1996 quatre colonies situées sur des îlots à faible couvert végétal et deux colonies situées sur des îles forestières. Trois traitements expérimentaux ont été appliqué faisant varier la fréquence et la période à l'intérieur de l'incubation où débutaient les visites. Chaque année, chacun des traitements utilisés étaient appliqués à plusieurs colonies d’eiders différant entre elles par la densité de goélands nicheurs sur la même île. Durant les visites, les observateurs vérifiaient si les nids suivis étaient toujours sous incubation, et plusieurs variables ont été mesuré décrivant la qualité des femelles (taille des couvées et date de ponte) et la qualité du site de nidification (dissimulation des nids, distance jusqu’ à la rive, hauteur de la végétation et la densité de goélands nicheurs sur l’île). La fréquence des visites n’influencait pas le succès de nidification puisque les nids qui ont échoué ont principalement été noté à la suite de la première visite. La période à l'intérieur de l'incubation où débutaient les visites était d'une grande importance; les visites hâtives ont plus fortement affecté la survie des nids d'eiders. La densités de goélands nicheurs était reliée au succès de nidification des eiders associés à la même île seulement lorsque les visites survenaient tôt durant l'incubation. Les femelle possédant un fort potentiel reproductif (caractérisées par une taille de couvée élevée et une date de ponte hâtive) sont celles qui ont le mieux réussi face à nos dérangements successifs. Ces femelles se trouvaient en plus forte proportion sur les îles associée aux plus faibles densités de goélands nicheurs; sur les îles ayant un couvert forestier plutôt que sur les îlots à faible couvert végétal. À l’intérieur d’une même colonie, ce type de femelles nichaient près de la rive où leurs nids étaient moins dissimulés. Les résultats démontrent que des visites de colonies d’eiders à duvet peuvent engendrer d’importantes pertes de nids. La situation la plus critique étant lorsqu’une visite survient tôt durant l’incubation sur les îlots à faible couvert végétal.


François Bolduc
Back to Top


Intraspecific nest parasitism in Red-breasted Mergansers (Mergus serrator)

Intraspecific nest parasitism is common among waterfowl. Several factors play a role in making parasitism more recurrent in ducks: Duck nests are easily detected by parasites, they have large clutches which hatch synchronously giving parasites many opportunities of unattended nests before the start of incubation, the presence of genetic relatedness among females may reduce the costs of being parasitized, and lastly, duck offspring are precocial, therefore parental costs are low, in turn lowering the costs of parasitism. The Red-breasted Merganser is amongst a list of birds involved in intraspecific nest parasitism, and the rate of  occurrence of this behaviour has been confirmed. However, as with other species, neither the identity or tactics of parasitic females have been confirmed. The objective of my study is to take the research on brood parasitism one step further and identify parasitic females within a Red-breasted Merganser colony, as well as determine the factors influencing this behaviour. In order to identify parasitic females, genetic analysis testing for parentage between incubating hens and the eggs in their nest, will be performed. Traditionally, this would involve having to take blood samples from all females and all chicks. For my research, I will be collecting and extracting DNA from nest materials, a method which is slowly proving to be more practical, since it does not involve any animal manipulation. The colony which will be studied is one which has been studied since the early 1980s, located in Kouchibouguac National Park, New Brunswick.

Le parasitisme intraspecifique au nid du bec-scie à poitrine rousse (Mergus serrator)

Le parasitisme intraspécifique au nid est trés commun chez les oiseaux aquatiques. Chez les canards, plusieurs facteurs encouragent ce comportement. 1) Les nids de canards peuvent être facilement repèrés par les parasites. 2) Les couvées sont volumineuses et éclosent en mode synchronisée permetant ainsi beaucoup de temps aux parasites de rajouter leurs propres oeufs à la couvée. 3) La présence d'un lien génétique parmi les canes peut réduire le coût d'être parasité par une consœur. 4) Enfin, les canetons sont nidifuges, donc l'investissement parental post-éclosion est faible, réduisant encore l'effet du parasitisme. Le Bec-scie à Poitrine Rousse fait parti d'un groupe d'oiseaux qui pratique le parasitisme intraspécifique au nid, et la fréquence de ce comportement a été confirmé. Cependant, en comparaison avec d'autres èspeces, ni l'identité, ni les tactiques employées par les femelles parasites ont été établis. Le but de ma recherche est: 1) Identifier les canes parasites parmi une colonie de Bec-scie à Poitrine Rousse, et 2) établir les facteurs qui les poussent à adopter ce comportement. Afin d'identifier les canes parasites, à l'aide des sondes géniques nous essayerons d'établir un lien de parenté entre les canes couveuses et les oeufs des nids. Sans avoir à recourir aux véniponctions, l'extraction d'ADN sera faite à partir de débris de plumes et/ou membranes d'oeufs vides, une fois le nid déserté. La colonie ciblée pour l'étude se situe dans le Parc National de Kouchibouguac au Nouveau-Brunswick.

Jovette Bouchard
Back to Top
 

Diet and breeding biology of Herring Gulls in the Mingan Archipelago National Park Reserve

Breeding biology and diet of Herring Gulls (Larus argentatus) were studied on Île Nue, in the Mingan Archipelago National Park Reserve, in the Gulf of St. Lawrence.  Nesting parameters were measured 1994-1996, and fledging success and diet were followed in 1996. Clutch size was low in all three years of the study, and hatching success was low in 1995. Low clutch size and hatching success could not be explained by researcher disturbance, predation, or competition for nest sites, leaving food-stress as the most likely explanation. To reduce the biases associated with determining diet, we used four methods to estimate diet. The 1996 breeding season was divided into three periods using changes in the number of gull pellets collected from roost sites as an indirect measure of dietary changes; these periods corresponded to the pre-spawning, spawning, and post-spawning periods of capelin (Mallotus villosus). At the beginning of the season, Herring Gulls fed mainly on intertidal prey, insects, and artificial food sources; in the middle of the breeding season, when capelin were spawning, the colony switched to feeding mainly on capelin; and at the end of the season, the colony fed almost entirely on crowberries (Empetrum nigrum). In 1996, productivity was followed for pairs of Herring Gulls whose clutch sizes were artificially increased and decreased to alter the parental effort required to raise a brood. Clutch manipulations did not affect chick growth, and fledging success was affected more by a food shortage late in the season than by manipulations. When capelin were spawning, there was an abundance of food and Herring Gull chicks grew normally, however, 80% of the chicks that were followed died of starvation in the four week period following the departure of capelin.  Body condition of adults was significantly lower after the capelin moved offshore and over half of the chicks that fledged were later found dead. Possible explanations for the low productivity include decreased availability of artificial food sources because of reductions in fisheries discards due to quota restrictions, and changes in the abundance of capelin or timing of spawning due to oceanographic variability.

Le régime alimentaire et la biologie de la période d'élevage du goéland argenté à l'intérieur de la réserve du parc National de l'Archipelago de Mingan

La biologie de reproduction et le régime alimentaire du Goéland argenté Larus argentatus furent étudiés sur l’Île Nue, dans la Réserve de Parc national Archipel-de-Mingan, dans le Golfe du Saint-Laurent.  Les paramètres de nidification furent mesurés de 1994-1996, et la productivité à l’envol et le régime alimentaire furent estimés en 1996.  La taille des couvées fut basse pendant les trois années de l’étude, et le succès d’éclosion fut bas en 1995.  La basse taille des couvées et le faible succès d’éclosion ne s’expliquaient pas par les perturbations des chercheurs, la prédation, ou la compétition pour les sites de nidification.  Une explication plus probable de la cause de ces résultats était la faible disponibilité de nourriture. Afin de réduire les biais associés à l’analyse du régime alimentaire, nous avons utilisé quatre méthodes pour estimer le régime alimentaire.  La saison de reproduction de 1996 fut divisée en trois périodes basées sur les changements du nombre de boulettes de goélands recueillies dans les perchoirs qui agissait comme mesure indirecte des changements diététique.  Ces périodes correspondaient aux périodes de pré-frai, de frai, et de post-frai du capelan Mallotus villosus. Au début de la saison, les Goélands argentés se nourrissaient surtout de proies intertidales, d’insectes, et de sources artificielles de nourriture.  Au milieu de la saison de reproduction, lors de la période de frai du capelan, la colonie a passé à se nourrir principalement de capelan.  Vers la fin de la saison, la colonie se nourrissait presqu’entièrement de caramine noire Empetrum nigrum.  En 1996, la productivité fut suivi chez des couples de Goélands argentés dont la taille des couvées fut augmentée ou diminuée artificiellement, afin de modifier le niveau d’effort parental requis pour élever les poussins.  Les manipulations des couvées n’ont pas affecté le taux de croissance des poussins, et le manque de nourriture vers la fin de la saison eut un effet plus marqué sur la productivité à l’envol que les manipulations.  Lors de la frai du capelan, il y avait une abondance de nourriture, et les poussins des Goélands argentés grandissaient de façon normale.  Cependant, 80% des jeunes que l’on a suivi sont morts de faim lors de la périodes de quatre semaines qui suivi le départ du capelan.  La condition corporelle des adultes fut significativement plus basse une fois le retour en mer du capelan, et plus de la moitié des poussins qui avaient survécu à l’âge d’envol ont été trouvés morts.  Les explications possibles pour le faible taux de productivité incluent le déclin de la disponibilité des sources artificielles de nourriture suite à la réduction de déchets des pêcheries due à la restriction des quota de pêche, ainsi que des changements dans l’abondance du capelan ou du moment de la frai dues à la variabilité océanographique.


Andrew Boyne
Back to Top

 

The ecology of the Sharp-shinned Hawk (Accipiter striatus) in southern Quebec

    Although the Sharp-shinned Hawk (Accipiter striatus) is one of the most common and widespread North American raptors, its population numbers across its range are not known. Largely this is because this species is so secretive and widely dispersed, making it difficult and expensive to census its populations. Its migratory routes are therefore very important to wildlife managers, who try to infer population numbers from the counts of birds observed at traditional watch sites each autumn.
    Northeastern populations use two main flyways for their southward fall migration - some birds skirt the easternmost ridge of the Appalachians, and others follow the Atlantic coast. During the 1980's and 90's, observers along these two routes reported that the numbers of migrating Sharp-shinned Hawks were decreasing, while observers along routes used by more western populations were recording either stable or increasing numbers for the same period of time.

    These observations have led researchers to speculate on the reasons behind the apparent declines in northeastern migrants. Some have suggested that this trend is indicative of changes in migratory routes or behaviour such that increasing numbers of individuals remain on their breeding grounds well into the winter. If so, this could be related to the growing popularity of bird feeding. This would make northern areas more attractive to Sharp-shinned Hawks, which are among the most common predators of birds at feeders. On the other hand, the declining numbers of migrants may reflect true population trends. If this is the case, maybe the reproductive success of northeastern populations is decreasing due to one or more factors such as exposure to pesticides and the loss of suitable breeding habitats due to urbanization.

     The basic issue of whether the declines reflect actual population trends or changes in migratory patterns and winter distributions is yet to be resolved, as is the possibility that the reproductive success of the Sharp-shinned Hawk is decreasing. Accordingly, the overall aim of this study is to shed some light on the impacts of human activity, including the continuing release of pesticides into the environment, urbanization and the increasing popularity of bird feeding, on the Sharp-shinned Hawk population in southern Quebec.

   This study includes several specific components. The first objective is to evaluate the reproductive success of this population in comparison to that of its counterparts elsewhere, by measuring various reproductive parameters, including clutch size, hatching success, and fledging success at nests in the Montreal area. The next task will be to determine the extent to which the birds are being affected by toxic chemicals, by taking blood samples from nesting parents and their young, as well as unhatched eggs from the nests, and submitting all these tissues for toxicological analysis by the Canadian Wildlife Service. As a small side project, small sub-samples of blood will be submitted for genetic analysis to investigate the question of genetic parentage and to determine whether any extra-pair fertilizations have taken place among these birds. While many studies have revealed that birds in general are far more promiscuous than they were previously believed to be, research conducted on several raptorial species has shown that extra-pair fertilizations are relatively rare. However, mate fidelity among Sharp-shinned Hawks has not yet been studied and taking blood samples for toxicological analysis will provide a perfect opportunity to look at this aspect of their ecology. In the next phase of this study, radio-tracking will be used to monitor the movements and foraging behaviour of individuals trapped at feeders in the winter. Hopefully this will indicate whether Sharp-shinned Hawks wintering in the Montreal area are hunting mainly at feeders, and whether they frequent certain feeders more than others, and if they do, what features make these locations particularly appealing. Finally, this study aims to characterize the nesting habitats being used by these birds, in comparison to those being used by other populations, by measuring various habitat variables in a plot centered on the nest tree. The goal is to see whether this population differs from others in its plasticity with respect to the use of nesting habitats. Preliminary results have shown that this population is using more mature stands than other populations are, but additional data is required to establish whether these findings are statistically significant.

Joanna Coleman
Back to Top

 

Effects of electric and magnetic fields on selected physiological and reproductive parametres of American Kestrels

    Birds nest under electric and magnetic fields (EMFs) generated by transmission lines, which may affect their reproductive success and/or melatonin governing their circadian and circannual cycles. Over two years, captive kestrels were used to determine whether EMFs affect their plasma melatonin concentrations and their reproductive success. EMFs were equivalent to that which wild kestrels are exposed to while nesting under 735 kV transmission lines, and daily exposure used in the captive study (88 - 98% time budget) was  potentially equivalent to that of wild kestrels (90%, 80% male). Captive kestrels were housed in control or EMF conditions to determine short-term (one season; S-EMF) and longer-term EMF (two seasons; L-EMF) effects.  Plasma melatonin in adult EMF males was suppressed at 42 d and elevated at 70 d of EMF exposure compared to controls. Melatonin levels in EMF males at mid-season were similar to controls at season's end, suggesting a seasonal phase-shift. Melatonin was suppressed in L-EMF fledgling birds but not in adult females or males (1995) at 70 d. Plasma melatonin, higher in adult males than females at 70 d post-pairing, was not directly associated with body mass changes in kestrels. Captive EMF birds were more active and alert but groomed less often than controls. EMF exposure affected reproductive success of kestrels. Fertility and fledging success were higher, and hatching success lower in S-EMF clutches. Hatching success was higher, but fledging success lower in L-EMF clutches. In S-EMF clutches, mean egg volume and mass were greater, eggs had slightly more albumen but thinner eggshells, and embryos were larger than controls.  L-EMF hatchlings were heavier than controls.  The melatonin results for male kestrels indicate that kestrels perceive EMFs as light, thus altering their photoperiod. Photoperiodic manipulations advance molt onset, which is associated with increased body mass in male kestrels. S-EMF males were heavier at 56 d of exposure when molt began, but this was unlikely related to feed intake which was unchanged. EMF exposure had no effect on body mass and pectoral muscle scores of reproducing females. The sexually-dimorphic response in body mass and melatonin concentrations suggests that male kestrels may be more sensitive to EMF exposure than females.

Les effets des champs électriques et magnétiques sur les crécerelles sauvages et captives

    Les oiseaux nichent sous les lignes électriques qui génèrent des champs électro- magnétiques (CÉM) pouvant affecter leur succès de reproduction et/ou les cycles circadiens et circannuels gouvernés par la mélatonine. Sur une période de deux ans, des faucons crécerelles élèvés en captivité ont été utilisés pour déterminer si les CÉM affectaient les concentrations de mélatonine du plasma et le succès reproducteur. Les CÉM étaient équivalents à ceux générés par des lignes de 735 kV sous lesquels des crécerelles nichent. La durée d'exposition à ces CÉM était potentiellement équivalente (88%-98% du budget-temps)  à celle observée en nature (femelles 90%, mâles 80%). Les faucons captifs étaient assignés soit comme témoins, soit soumis à des CÉM pour déterminer les effets à court terme (une saison; CÉM-court) et à long terme (2 saisons; CÉM-long).  La mélatonine plasmatique était supprimée chez les mâles adultes à 42 jours d'exposition aux CÉM mais supérieure aux témoins à 70 jours d'exposition. Les taux de mélatonine des mâles sous CÉM à mi-saison étaient équivalents à ceux des témoins en fin de saison, suggérant la présence d'un changement de phase saisonnier. La mélatonine était supprimée chez les oisillons après l'envol sous traitement CÉM-long, mais pas chez les mâles et les femelles adultes (1995) exposés 70 jours. La mélatonine plasmatique, plus élevée chez les mâles que chez les femelles 70 jours après la formation des paires, n'était pas directement associée avec les changements de poids observés.  Les oiseaux captifs exposés à des CÉM étaient plus actifs et plus alertes que les individus témoins, mais se nettoyaient les plumes moins souvent. L'exposition aux CÉM a affecté le succès de reproduction des faucons. Pour les couvées sous CÉM-court, la fertilité et le nombre d'oisillons à l'envol étaient plus élevés, mais le taux d'éclosion plus bas que chez les témoins. Pour les couvées sous CÉM-long, le taux d'éclosion était plus élevé, mais le nombre d'oisillons à l'envol plus bas. Pour les couvées CÉM-court, le volume et le poids moyens des oeufs étaient plus élevé, les oeufs contenaient un peu plus d'albumen mais une coquille plus mince, et les embryons étaient plus gros que chez les témoins. Les oisillons éclos sous CÉM-long étaient plus lourds que les témoins.  Les données concernant la mélatonine indiquent que les crécerelles mâles perçoivent les CÉM comme la lumière, ceux-ci affectant la photopériode. Chez les mâles, la manipulation de la photopériode avance la mue, associée à un accroissement du poids. Les mâles sous CÉM- court étaient plus lourds à 56 jours d'exposition quand la mue a commencé, sans relation apparente avec la prise de nourriture qui n'avait pas changé. L'exposition aux CÉM n'a pas affecté le poids corporel et le volume des muscles pectoraux des femelles reproductrices. La différence de réponse selon le sexe, au niveau du poids corporel et des concentrations de mélatonine, suggère que les mâles seraient plus sensibles que les femelles à une exposition aux CÉM.

Kim Fernie
Back to Top


Raptor foraging ecology in prairie landscapes managed for enhanced waterfowl recruitment

Great Horned Owls (GHO) (Bubo virginianus) and Red-tailed Hawks (RTH) (Buteo jamacencis) are nocturnal and diurnal predators for which ducks can be important prey during their breeding seasons. The major objective of this study was to identify factors associated with variation in raptor prey selection, especially those related to predation on waterfowl. We examined the impact of variation in landscape characteristics, waterfowl density and density of alternate prey upon the diet of the above raptors. A second objective was to determine which ecological factors affect the density and distribution of raptors at a landscape level.
The study was conducted at Prairie Habitat Joint Venture assessment sites in Saskatchewan. In 1997, two sites were studied, the Allan Hills and Willowbrook sites whereas in 1998 only one site was studied, the Jumping Deer Creek site. In 1999, another site in the Allan Hills was studied. Intensive foot and roadside surveys were used to locate all the raptor nests. Waterfowl population data were collected by IWWR (Institute for Wetland and Waterfowl Research) staff. Small mammal densities were gathered through another concurrent study. Densities of other potential prey were assessed through various transect techniques in appropriate habitats. Indices of prey availability will be derived from measures of prey density and vegetation cover. Prey remains and pellets were collected in and around GHO and RTH nests to determine diet. In addition, observations of prey brought to nestlings by adults were conducted from blinds on a sample of RTH nests. Diet preferences will be determined from comparison of prey consumption versus availability. Regression techniques will be used to assess the influence of habitat characteristics on diet and raptor reproductive success.  Statistical models will be used to examine relationships between habitat variables, prey selection, raptor densities and productivity.

Alain Fontaine and Marc Pauzé
Back to Top

 

The adrenocorticol stress response in captive juvenile American Kestrels (Falco sparverius): changes over development

    Many avian behavioural patterns, such as breeding, migration and territoriality, are correlated with changes in hormonal levels. Elevated levels of corticosterone, an adrenal steroid hormone, are associated with increased foraging, increased activity levels and response to stressful situations in birds. Because of predation risk, young of open-nesting species are expected to have an hypothalomo-pituitary-adrenal (HPA) axis which develops more quickly that of than cavity-nesting young whose risks generally occur only once they have fledged and left the confines of the nest.

The adrenal stress response was examined in developing nestling American kestrels (Falcospaverius), cavity nesters which typically depart from the nest between 25-30 days of age. Circulating corticosterone levels are being measured from serial blood samples for chicks of 10, 16, 22 and 28 days of age which underwent a standardized handling and restraint protocol known to elicit a classical increase in the circulating hormone, corticosterone. This "capture stress" has been applied to a wide spectrum of species looking at a number of factors known to affect the HPA axis of the adrenal gland.

The subsequent rise of plasma corticosterone levels following capture will be an indication of the sensitivity of the HPA axis. Plasma levels of corticosterone will be measured using radioimmunoassay. Results should indicate at which age the HPA axis is sufficiently developed to allow juveniles to deal with acute stress, as well as indicating the most sensitive periods of development.

Effects of Captivity on the Adrenal Stress-Response in American Kestrels (Falco sparverius)

    Facilities such as research and zoological centres which house animals for extended periods of time in captivity are often faced with the question of whether captivity causes undo levels of stress to its inhabitants. Recent work has found long-term decreases in circulating corticosterone in captive shorebirds. The possible reason may be that the birds recognize captive conditions as normal and predictable. The Avian Science and Conservation Centre of McGill University houses over 350 American kestrels ranging in age from 3 months to 8 years of age making it a perfect system to study the effects of constant captive conditions on the hypothalo-pituitary-adrenal (HPA) axis in birds.

The adrenal gland is responsible for aiding a bird in responding to stressful situations such as predators and harsh environments such as bad weather. The gland has been hypothesized to atrophy in situations where conditions are constant and therefore less "stressful". Consequently, one should find a gradation of decreased stress-responses of birds in relation to how long they have been kept under constant housing and feeding conditions.

    Circulating corticosterone levels were measured from serial blood samples for birds aged 1 month to 6 years which underwent a standardized handling and restraint protocol known to elicit a classical increase in the circulating hormone, corticosterone. This "capture stress" has been applied to a wide spectrum of species  looking at a number of factors known to affect the HPA axis of the adrenal gland. The subsequent rise of plasma corticosterone levels following capture will be an indication of the sensitivity of the HPA axis. Upon preliminary analysis, stress responses do appear to be correlated to length of time in captivity; decreasing as time in captivity increases. Although this may be due to handling over time, as well as acclimation to captive conditions, it still has implications as to whether captivity is truly stressful to its inhabitants.

The effects of PCB's on the function of the hypothalamo pituitary-adrenal (HPA) axis in captive American Kestrels (Falco sparverius)

    Although the adrenal gland has been shown to accumulate lipophilic compounds such as organochlorine contaminants and poly-chlorinated biphenyls (PCB's) in many groups of fish and amphibians, work has not yet centred upon the effects of these contaminants on high order predatory birds. Based on the high susceptibility of the adrenal gland to toxicological insult, deregulation of the HPA axis by PCB's may have serious effects on a birds' ability to adequately deal with environmental stresses.

    Using captive American kestrels exposed to high doses of PCB's during a previous study, standardized methods were used to evaluate the response of PCB-contaminated and control birds to a defined physical stressor.The subsequent rise of plasma corticosterone levels following capture  is an indication of the sensitivity of the HPA axis to the toxicological insult of PCB contaminants.

    Results of this study indicate a positive relationship between contaminant level and the levels of circulating corticosterone (sensitivity of HPA axis). Stress responses of PCB-contaminated birds were significantly lower from those of control birds for both baseline and maximum measures of corticosterone.  This establishes that alterations in HPA axis function and regulation of intermediary metabolism are correlated with exposure to contaminants in birds and determine what danger they play in endocrine disruption.  Results provide some of the first concrete evidence that human-made contaminants deleteriously affect the endocrine systems of birds feeding at high trophic levels such as birds of prey and colonial fish-eating species.

Oliver P. Love
Back to Top


The role of birds as predators and potential biocontrol agents of insect pests in corn fields

This project investigated the impact on insect pests of excluding birds from portions of two cornfields through the use of bird-proof netting. Rhopalosiphum maidis, Ostrinia nubilalis, Agrotis spp. and Sphenophorus spp. were all found in higher density in plots where birds were excluded.  Only the adult Diabrotica longicomis population was not reduced by birds.  Results suggest that birds can reduce insect pest populations.  Bird visits in cornfields with respect to distance from field edge, type of edge habitat habitat and corn phenology were also studied. Red-winged Blackbird (Agelaius phoeniceus), Song Sparrow (Melospiza melodia), Chipping Sparrows (Spizella passerina passerina) and American Robin (Turdus migratorius) were the most frequently observed bird species inside cornfields.  Early in the summer, birds tended to stay closer to the edge, especially for an edge composed of mature coniferous trees. Different bird species visited cornfields at specific periods during corn development.  Field edge habitats and composition affected bird numbers inside the cornfields.

Le rôle des oiseaux en tant que prédateurs et agents de biocontrole potentiels sur les insectes nuisibles à l'intérieur des champs de maïs

L'objectif de ce projet de recherche était de déterminer l'impact des oiseaux sur les populations d'insectes nuisibles du maïs.  Rhopalosiphum maidis, Ostrinia nubilalis, Agrotis spp. et Sphenophorus spp. furent échantillonés en plus grand nombre dans les parcelles sans oiseaux.  Diadrotica longicornis n'a pas été affectée par la présence des oiseaux.  Les oiseaux peuvent donc diminuer les populations d'insectes nuisibles.  Les visites d'oiseaux dans les champs ont aussi été étudiées.  Le carouge à épaulettes, les bruants chanteurs et familiers et le merle d'Amérique étaient les espèces d'oiseaux les plus fréquemment observées dans les champs.  En générale, les oiseaux restaient plus près de la bordure du champs, surtout tôt durant l'été et dans le champs près des conifères.  Selon la croissance du maïs, différentes espèces d'oiseaux fréquentaient les champs de maïs.  La composition et le type de lisière en bordure d'un champ affectent l'abondance des oiseaux à l'intérieur des champs de maïs.

Annie Tremblay
Back to Top

 

 

 
 

Return to ASCC Homepage
 

© 2003 Avian Science and Conservation Centre
McGill  University, 21,111 Lakeshore Rd.
Ste-Anne-de-Bellevue, Québec,  Canada H9X 3V9
Phone: (514) 398-7760     Fax: (514) 398-7990
Webmaster