Factors influencing the growth of Bald Eagles in north central Saskatchewan

1989 ◽  
Vol 67 (3) ◽  
pp. 606-611 ◽  
Author(s):  
Gary R. Bortolotti
Keyword(s):  
Hatching Asynchrony ◽  
Haliaeetus Leucocephalus ◽  
Relative Timing ◽  
Bald Eagles ◽  
Fish Prey ◽  
North Central ◽  
Factors Influencing ◽  
Lower Productivity ◽  
Absolute Growth ◽  
High Fish

Mass and eighth primary growth of nestling Bald Eagles (Haliaeetus leucocephalus) were studied in north central Saskatchewan from 1980 to 1982. There were no significant differences among years for any measure of growth. Clutch size and the relative timing of hatching within each breeding season also had no effect on growth. In broods of two young, second-hatched chicks (C2) grew slower than first-hatched chicks (C1) if the hatching interval between siblings was 2 days rather than 1 day. As both hatching asynchrony and the degree of suppressed growth of C2 were independent of absolute growth rates (and hence presumably food supply), it was unlikely that individual females modified the degree of asynchrony in any adaptive manner. Nestlings raised in an area predicted to have high fish (prey) productivity, given the morphology and chemistry of the lake, grew faster than chicks in an area of lower productivity. Growth rate was significantly correlated with the total mass of prey, but not the number of prey items, delivered to the nests by the parents.

Frequency of Protocalliphora avium (Diptera: Calliphoridae) infestations on bald eagles (Haliaeetus leucocephalus)

1985 ◽  
Vol 63 (1) ◽  
pp. 165-168 ◽  
Author(s):  
Gary R. Bortolotti
Keyword(s):  
First Record ◽  
Seasonal Effect ◽  
Haliaeetus Leucocephalus ◽  
Behavioural Development ◽  
Bald Eagles ◽  
North Central ◽  
Factors Associated ◽  
Large Numbers ◽  
Nestling Period

This is the first record of nestling bald eagles as hosts of the parasitic blowfly Protocalliphora avium (Diptera: Calliphoridae). The frequency of infestation of the hematophagous larvae was determined by repeatedly examining eaglets over the entire 10- to 12-week nestling period from 1980 to 1982 in north-central Saskatchewan. Seventy-two nestlings were examined a total of 461 times. All nestlings less than 49 days old were parasitized by large numbers of larvae in the aural cavities, on the nape of the neck, and on the top of the head. The frequency of parasitism was high from the time the eaglets hatched until they were 16 days old when it sharply declined. The birds were repeatedly infested, suggesting that P. avium may have been an intermittent feeder. There was no difference between the frequency of infestation in nests containing one or two chicks, nor between the first-hatched and second-hatched eaglet within a brood. Factors associated with the physical and behavioural development of the eaglets, rather than a seasonal effect on the parasites, may account for the decline and cessation of infestation.

scholarly journals Effects of Nesting Bald Eagles (Haliaeetus leucocephalus) on Behaviour and Reproductive Rates in a Great Blue Heron (Ardea herodias) Colony in Ontario

2018 ◽  
Vol 131 (4) ◽  
pp. 369-371
Author(s):  
Bill Thompson
Keyword(s):  
Single Species ◽  
Mortality Rates ◽  
Haliaeetus Leucocephalus ◽  
Bald Eagles ◽  
Fish Prey ◽  
Movement Rates ◽  
Ardea Herodias ◽  
Great Blue Heron ◽  
Significant Difference ◽  
Reproductive Rates

Bald Eagles (Haliaeetus leucocephalus) and Great Blue Herons (Ardea herodias) are known to occasionally nest in mixed colonies, even though the former is one of the primary predators of the latter. I observed the two species in four heron colonies near Lake Simcoe, Ontario during two field seasons to assess whether rates of heron chick mortality or nest abandonment were greater in a colony that supported a nesting pair of Bald Eagles than in three nearby single-species colonies. I assessed the effects of eagle presence on heron behaviour using heron movement rates, the number of heron sentries left in colonies during the nesting period, heron nest mortality rates, and the average number of successfully fledged herons per nest. There was no statistically significant difference in movement rate among the four colonies, proportion of birds remaining as sentries, nor nest mortality rates. However, nests in the mixed colony successfully fledged significantly more heron young per nest than did nests in the single-species colonies. The mixed colony was located in a wetland and open lake system that provided extensive foraging habitat and an abundance of the preferred fish prey species of both Great Blue Herons and Bald Eagles, thus reducing predation pressure on the herons.

Winter Roosting Patterns of Bald Eagles (Haliaeetus leucocephalus) in North-Central Arizona

1989 ◽  
Vol 34 (4) ◽  
pp. 453 ◽  
Author(s):  
Teryl G. Grubb ◽  
Sandra J. Nagiller ◽  
Wade L. Eakle ◽  
Gregory A. Goodwin
Keyword(s):  
Haliaeetus Leucocephalus ◽  
Bald Eagles ◽  
North Central ◽  
Central Arizona

scholarly journals Ecological interactions and habitat modification in nesting Common Murres, Uria aalge

1996 ◽  
Vol 6 (3) ◽  
pp. 261-269 ◽  
Author(s):  
Julia K. Parrish ◽  
Robert T. Paine
Keyword(s):  
Reproductive Output ◽  
Habitat Modification ◽  
Haliaeetus Leucocephalus ◽  
Uria Aalge ◽  
Ecological Interactions ◽  
Bald Eagles ◽  
Predator Removal ◽  
Common Murre ◽  
Corvus Caurinus ◽  
Common Murres

SummarySeabird populations suffer from a variety of natural and human-induced sources of mortality and loss of lifetime reproductive output. On the outer coast of Washington State, Common Murre Uria aalge populations have been in decline for approximately the last decade and are currently reproductively active only at Tatoosh Island. These murres nest in two basic habitat types: crevices (25% of the population) and larger cliff-top subcolonies (75%). Murres in cliff-top subcolonies have suffered dramatic reductions in reproductive success in recent years relative to conspecifics nesting in the crevices, primarily due to egg predation by Glaucous-winged Gulls Larus glaucescens and Northwestern Crows Corvus caurinus, facilitated by the presence of Bald Eagles Haliaeetus leucocephalus. Because predator removal is not feasible and creation of additional crevice habitat is difficult, expensive and potentially ineffective, we have designed a temporary habitat modification (the “silk forest”) which replaces the natural vegetation cover and modifies the interaction between murres and eagles. Within the test subcolony, murres nesting under and immediately adjacent to the silk forest produced nearly twice as many eggs per square metre as their conspecifics nesting in adjacent exposed-ground areas.

Reproductive success of bald eagles (Haliaeetus leucocephalus) and its association with habitat or landscape features and weather in southeast Alaska

1997 ◽  
Vol 75 (10) ◽  
pp. 1595-1604 ◽  
Author(s):  
Scott M. Gende ◽  
Mary F. Wilson ◽  
Mike Jacobsen
Keyword(s):  
Early Spring ◽  
Average Density ◽  
Nesting Success ◽  
Egg Laying ◽  
Haliaeetus Leucocephalus ◽  
Bald Eagles ◽  
Active Nest ◽  
Southeast Alaska ◽  
Landscape Features

Long-term data have been collected on nesting bald eagles (Haliaeetus leucocephalus) in three areas of southeast Alaska. The average density of active nests was among the highest recorded, but nest productivity (average number of young fledged per active nest) and success (percentage of active nests that fledged at least one young) were similar to values in other areas. Using logistic regression, nest productivity was associated with several habitat or landscape features (productivity was highest in proximity to spawning herring and at a particular location), each of which could be related to the availability of prey (fish) in the early spring (April, May) during egg laying and incubation. Consistency of nesting success was associated with the presence of tidal flats at one study site. Nest use, but not nesting success, was related to nesting success the previous year. Multiple regression showed that fewer nests per kilometre were successful in years with a high frequency of spring rains.

Bald Eagle Lead Exposure in the Upper Midwest

2014 ◽  
Vol 5 (2) ◽  
pp. 208-216 ◽  
Author(s):  
Sarah E. Warner ◽  
Edward E. Britton ◽  
Drew N. Becker ◽  
Michael J. Coffey
Keyword(s):  
Lead Poisoning ◽  
Lead Exposure ◽  
Clinical Signs ◽  
Local Environment ◽  
Bald Eagle ◽  
Haliaeetus Leucocephalus ◽  
Upper Midwest ◽  
Bald Eagles ◽  
Potential Source ◽  
Liver Lead Concentration

Abstract In 2012, we examined lead exposure in 58 bald eagles Haliaeetus leucocephalus found dead in Iowa, Minnesota, and Wisconsin. We determined lead concentrations in livers, examined differences in exposure among ages and between sexes, and recorded clinical signs consistent with lead poisoning. Most (60%) of the bald eagles had detectable lead concentrations, and 38% of the 58 had concentrations within the lethal range for lead poisoning. We found no differences in exposure based on sex or age, but we did find an inverse relationship between body and liver mass and liver lead concentration. The high percentage of lead-exposed bald eagles encouraged us to further examine potential sources of lead in our local environment. We initiated a study on the Fish and Wildlife Service's Upper Mississippi River National Wildlife and Fish Refuge to investigate if discarded offal piles from hunter-killed deer were a potential source of lead exposure to scavenging wildlife such as the bald eagle. Radiographs showed that 36% of offal piles in our sample area contained lead fragments ranging from 1 to 107 particles per pile. Our study indicated that 1) lead exposure rates for bald eagles found dead in our Upper Midwest study area were high, 2) more than one-third of the bald eagles found dead in Iowa, Minnesota, and Wisconsin had liver lead concentrations consistent with lead poisoning, and 3) discarded offal piles from deer shot with lead ammunition can be a potential source of lead exposure for bald eagles.

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