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A photographic and behavioral guide to aging nestling northern goshawks

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Clint W. Boal at Texas Tech University
Clint W. Boal
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Abstract

Observations of behavioral and morphological development of nestling Northern Goshawks (Accipiter gentilis) were collected during three nesting seasons at 20 goshawk nests in northern Arizona. A photographic record of a single nestling goshawk's development was made. I combined descriptions of age-specific behaviors exhibited by nestlings with descriptions and photographs of nestling mor- phological development to construct an aging guide for nestling Northern Goshawks. Adult goshawk behaviors that relate to nestling age are also provided. Accurate estimates of the ages of nestling rap- tors are important for scheduling banding (Fyfe and Olendorff 1976) and assessing productivity (Moritsch 1983a, b; Steenhof 1987, Young and Kochert 1987). Photographic guides to morpho- logical changes that occur as nestlings age have been developed for Prairie Falcons (Falco mex- icanus), Red-tailed Hawks (Buteo jamaicensis), and Ferruginous Hawks (B. regalis) (Moritsch 1983a, b; 1985), but are unavailable for most species. Because the behavior of young raptors is cor- related with age (e.g., Ellis 1979), descriptions of ~e-specific behaviors coupled with pictorial and verbal descriptions of morphological changes provide a more robust guide to aging nestling raptors. In addition, the behavior of the adult female changes with the age of nestlings and may be useful in evaluating nestling ages. Schnell (I 958) provided a written description of the development of nestling Northern Gos- hawks (Accipiter gentilis) at a single nest. Obser- vations of nestling development from several nests may provide a better understanding of the age ranges over which behavioral ontogeny oc- curs. I provide a photographic and behavioral guide to estimating the age of nestling Northern Goshawks.
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Studies in Avian Biology No. 16:32-40, 1994.
A PHOTOGRAPHIC AND BEHAVIORAL GUIDE TO AGING
NESTLING NORTHERN GOSHAWKS
CLINT W. BOAL
Abstract. Observations of behavioral and morphological development of nestling Northern Goshawks
(Accipiter gentilis) were collected during three nesting seasons at 20 goshawk nests in northern Arizona.
A photographic record of a single nestling goshawk's development was made. I combined descriptions
of age-specific behaviors exhibited by nestlings with descriptions and photographs of nestling mor-
phological development to construct an aging guide for nestling Northern Goshawks. Adult goshawk
behaviors that relate to nestling age are also provided.
Key Words: Accipiter gentilis; ageguide; nestling development; nestling behavior; Northern Goshawk.
Accurate estimates of the ages of nestling rap-
tors are important for scheduling banding (Fyfe
and Olendorff 1976) and assessing productivity
(Moritsch 1983a, b; Steenhof 1987, Young and
Kochert 1987). Photographic guides to morpho-
logical changes that occur as nestlings age have
been developed for Prairie Falcons (Falco mex-
icanus), Red-tailed Hawks (Buteo jamaicensis),
and Ferruginous Hawks (B. regalis) (Moritsch
1983a, b; 1985), but are unavailable for most
species.
Because the behavior of young raptors is cor-
related with age (e.g., Ellis 1979), descriptions of
~e-specific behaviors coupled with pictorial and
verbal descriptions of morphological changes
provide a more robust guide to aging nestling
raptors. In addition, the behavior of the adult
female changes with the age of nestlings and may
be useful in evaluating nestling ages.
Schnell (I958) provided a written description
of the development of nestling Northern Gos-
hawks (Accipiter gentilis) at a single nest. Obser-
vations of nestling development from several
nests may provide a better understanding of the
age ranges over which behavioral ontogeny oc-
curs. I provide a photographic and behavioral
guide to estimating the age of nestling Northern
Goshawks.
STUDY AREA AND METHODS
The study was conducted on the North Kaibab Rang-
er District (NKRD), Kaibab National Forest, Coconi-
no County, Arizona. The NKRD is an area of ap-
proximately 259,000 ha located on the Kaibab Plateau
in northern Arizona. A detailed description of the study
area is provided in Boal and Mannan (this volume).
Nest observations were conducted at 20 Northern
Goshawk nests on the NKRD during the nesting sea-
sons of 1990, 1991, and 1992. Information on the
morphological and behavioral development of nestling
goshawks was collected during 1539 hours of obser-
vation (X
= 76.8 hour/nest :t 19.3 [SD». These ob-
servations were made from blinds located on the ground
or in trees a mean distance of 53 m (:t 17.6) from the
nest trees. Observation periods began in the afternoon
l
and continued until sundown, resuming at dawn until
the time of initiation the previous day.
Photographs used in this guide are of the largest of
3 nestlings in a nest that was not part of my study, but
was being used in a concurrent telemetry study (Bright-
Smith and Mannan, this volume). I estimated the date
of hatching as 20 June, based on behaviors exhibited
by the nestlings and the adult female. I took photo-
graphs at 5-day intervals, starting with 5 days of age
and continuing until 20 days of age.
At 18 days the adult female disappeared from the
nesting area. Radio telemetry indicated the adult male
goshawk remained in the nest area during the following
TABLE I. GLOSSARY OF TERMS USED IN TEXT AND
FIGURES
Auricular
The area of the invisible ear open-
ing just posterior to the eye
A young raptor that has left the
nest but not the nest tree
Small contour feathers of the
wings and tail
The top of the head
When a young bird leaves the nest
tree of its own volition for the
first time
The back of the head below the
occipital portion of the skull
A growing feather that is encased
in sheathing
The outer flight feathers of the
wing
Rapid movement and readjust-
ment of the head while visually
focusing on an object
Primary and secondary wing
feathers
Tail feathers
Feathers located in the shoulder
region
Inner flight feathers of the wing
Wax-like keratinous material that
encases and protects newly de-
veloping feathers
The feet and claws of a hawk
Brancher
Coverts
Crown
Fledge
Nape
Pin feather
Primaries
Rapid peering
Remiges
Rectrices
Scapulars
Secondaries
Sheathing
Talons
32
PHOTOGRAPHIC GUIDE TO AGING NESTLING GOSHA WKS-Boal 33
days, but nest observations revealed that he did not
care for the nestlings. At 20 days of age, the largest
nestling, a male, attacked his siblings. He killed and
cannibalized one sibling and forced the other to leave
the nest and fall to its death (Boal and Bacorn, in press).
The surviving nestling was removed from the nest and
transferred to a wildlife rehabilitator for care. A pho-
tographic record was continued during captivity at 2-day
intervals from 25 days of age to 39 days of age. Pho-
tographs of this bird were combined with the obser-
vational data from the other nests to provide this guide.
Table I contains a glossary defining morphological
and behavioral terms used in describing ages of nest-
lings.
RESULTS
When a goshawk nest area is entered by hu-
mans during the first 5 days following hatching,
adult females show a strong tendency to remain
on their nests. Afterwards, females typically flush
from nests, perch in nearby trees while vocaliz-
ing, and possibly make low passes at intruders.
Adult male goshawks are rarely seen in the nest
area except during food deliveries. After deliv-
ering food to the female away from the nest,
males will often visit the nest briefly during the
first 10 days following hatching.
It is difficult to determine the presence of nest-
lings prior to approximately 4 days old. At about
4 days of age nestlings begin attempting to def-
ecate over the nest rim, and their presence is
evidenced by minute specks of white excrement
on the nest rim but not on the ground below the
nest (Fig. 1). At about 9 days white-wash globs
will be present on the branches and the ground
below the nest (Fig. 2).
Nestlings remain totally white in their first na-
tal down until 14-17 days when the gray second
natal down and flight pin feathers begin to appear
(Fig. 3). Scapular and covert feathers start emerg-
ing between 19 and 22 days (Fig. 4). Rapid and
noticeable feather development begins at 24-26
days. At this age, scapular and covert feathers
are visible, and the auricular area is covered with
small black feathers (Fig. 5). At 28-30 days, dark
feathers appear along the nape, but the crown is
still downy. Feathering is also apparent along the
FIGURE I (top left). Goshawks at 4-7 days post-hatching. Morphological Characteristics: Nestlings are small
(approximately 13 cm long) and covered in white natal down. Behavioral Characteristics: Nestlings lie prostrate
and usually out of view below the nest rim. Occasionally the tops of their heads may be seen, especially when
the female is feeding them. Nestlings are poorly coordinated and move by scooting motions with the body in
contact with the substrate. Nestlings may give whistle-like beg calls during feeding. Nestling hawks are able to
excrete over the nest rim starting at 4-5 days old. Small dime-sized specks of white excrement may be visible
on the sticks of the nest or against the tree trunk, but usually not on the ground. The adult female is almost
continuously present and always broods the nestlings at night. She tends to remain motionless on the nest rather
than flush and give the alarm call when the nest is approached.
FIGURE 2 (bottom left). Goshawk at 9-12 days post-hatching. Morphological Characteristics: Nestlings are
15-18 cm long and covered in white down. Behavioral Characteristics: Nestlings are most often lying in the
nest cup out of view. Primary movements are to position themselves to be fed or to defecate over the nest rim.
Movements are by scooting motions. Nestlings possess good head coordination when feeding, but are weak and
often use their wings for balance and support when moving. Nestlings are able to excrete with greater power.
Whitewash specks are numerous and obvious on the ground and branches below the nest. The adult female is
usually present and broods the nestlings at night. She tends to flush from the nest and give the alarm call when
the nest is approached.
FIGURE 3 (top right). Goshawk at 14-17 days post-hatching. Morphological Characteristics: Nestlings are
approximately 20-23 cm long and have molted into their second natal down, which has a gray, woolly appearance.
Auricular area is still downy. Pin 'feather development ofthe remiges and rectrices is apparent, especially when
the wings are extended upward. As much as 1 cm of the feather may have erupted from the pin feather sheaths.
Behavioral Characteristics: Nestlings are able to walk on their tarso-metatarsus while extending their wings for
balance. They may stand for brief moments and look about the nest area. Nestlings begin making preening
motions at their breast and wings.
FIGURE 4 (bottom right). Goshawk at 19-22 days post-hatching. Morphological Characteristics: Auricular
area behind and below the eye is developing as a dark patch of small feathers. Remiges and rectrices are erupting
from pin sheaths and contrast markedly with the body down. Greater coverts, upper tail coverts, and scapular
feathers are starting to emerge anc;lappear as dark dots against the body down. Close observations of the ventral
feather tracts reveal dark pins beneath the down. Behavioral Characteristics: Nestlings can walk on their feet
and usually do not use their wings for balance. They will stand for longer periods and preen. Nestlings rapidly
flap their wings for short periods (3-5 seconds), especially following feeding. Nestlings may attempt to peck their
own bites of food when the female is feeding them.
l
34
STUDIES IN AVIAN BIOLOGY
NO. 16
PHOTOGRAPHIC GUIDE TO AGING NESTLING GOSHAWKS-Boal 35
36 STUDIES IN AVIAN BIOLOGY
NO. 16
FIGURE 5. Goshawk at 24-26 days post-hatching. Morphological Characteristics: Auricular area is now
covered with small black feathers. The head and neck are still downy, but sheathed feathers may be seen beneath
the down. Scapular feathers and wing coverts are visible and contrast against the natal down. Feathers of the
ventral tracts start emerging and under tail coverts may also appear. Nestlings are approximately 112adult size.
Behavioral Characteristics: Nestlings stand on the nest rim and observe the nest surroundings. They spend a
great deal of time preening and wing flapping. Nestlings start stretching their feet and legs and making fists of
the talons. They may start grabbing nest twigs with their feet. Nestlings may successfully feed themselves if the
food has no skin or has been opened up by an adult. The adult female is usually in the nest area but does not
brood or shelter nestlings at night except during wet or unseasonably cold weather.
-t
FIGURE 6 (top right). Goshawk at 28-30 days post-hatching. Morphological Characteristics: Dark feathers
emerge along the nape, but the crown is still downy. Covert and scapular feathers fill in the upper wing and
back areas. Breast feathers are filling in along the ventral tracts but the middle of the breast and belly is still
downy. The under and upper tail coverts and legs are predominately downy, but a few feathers may be present.
Behavioral Characteristics: Nestlings spend much of their time preening, and begin scratching their heads with
their talons. Foot grabbing of nest twigs and other objects increases. Nestlings are very attentive to their
surroundings and pay attention to adults exchanging prey away from the nest. Rapid peering and sleeping while
standing are new behaviors exhibited during this stage. The adult female is rarely at the nest but is in the nest
area and becomes defensive when the nest area is entered.
FIGURE 7 (bottom right). Goshawk at 32-34 days post-hatching. Morphological Characteristics: Dark feathers
have emerged on the crown and are beginning to emerge at the comer of the mouth. The back and dorsal side
of wings are 90% feathered. The breast is filling in with feather growth but is still downy in the center and on
the belly. The undertail coverts have filled in and feathers will be emerging on the thighs. The underwing area
is still downy. Rectrices are about 213adult length. Behavioral Characteristics: Nestlings readily feed themselves
when the female is not present and may fight aggressively over food. Nestlings will vigorously beat their wings
while hopping and running across the nest. Nestlings may start branching at about 34-35 days.
PHOTOGRAPHIC GUIDE TO AGING NESTLING GOSHA WK$-Boal 37
...
- ...
I
38
STUDIES IN AVIAN BIOLOGY
NO. 16
PHOTOGRAPHIC GUIDE TO AGING NESTLING GOSHA WKB-Boal 39
sides of the breast (Fig. 6). At 32-34 days dark
feathers emerge on the crown, and feathering of
the legs is visible (Fig. 7). Body feathering is near-
ly completed at 36-38 days, but downy areas
persist on the sides of the neck (Fig. 8). At 40
days the only visible down is along the underside
of the wings (Fig. 9).
DISCUSSION
Moss (1979) described weight gain in nestling
sparrowhawks (A. nisus) as being initially slow
for 4-6 days, followed by a 10-day period of
rapid weight gain, and then a return to slow weight
gain. Though the periods will vary with different
species, this is the general pattern of growth in
nestling raptors. Food shortages can depress
weight gain in nestling raptors (Newton 1986).
Food deprivation during the 18-20 day age pe-
riod may have affected negatively the growth and
development of the photographed nestling.
However, I estimate the nestling goshawk ex-
perienced food deprivation near the end of the
rapid weight gain period (Moss 1979). Potential
depression of the nestlings' development may
have been minimized by the timing of the food
shortage and the constant food supply provided
by the rehabilitator. Fault bars, a likely side effect
offood deprivation and stress, were not observed
in the nestlings' rectrices after feather growth was
complete (c. Van Cleeve, Icarus Foundation,
pers. comm.). The photographic record agrees
with the observational data of nestling devel-
opment collected at the other nests used in this
study.
Reported fledging ages of nestling goshawks
are variable. Reynolds and Wight (1978) found
that nestling goshawks in Oregon fledged at 34-
37 days. Newton (1979) reported goshawks
fledged at 40-43 days, and Brown and Amadon
(1968) reported nestlings fledging as late as 45
days. Variation in fledging ages may be related
to nestling condition, geographical location, or
different definitions of branching and fledging. I
define 'branching' as when a nestling leaves the
nest but remains in the nest tree, and 'fledging'
as when a nestling first leaves the nest tree on its
own volition. Reynolds and Wight (1978) found
that male nestlings develop and fledge earlier than
females. In northern Arizona, male nestlings
usually fledged at about 38 days (range = 36-40
days), whereas female nestlings fledged at 39-42
days.
ACKNOWLEDGMENTS
I am grateful to B. Baker, B. Bibles, E. Bibles, R.
Brown,M. Collins,N. Karnovsky,R. W.Mannan, and
E.Steadmanforassistingwithnestobservations.Ithank
J. Dawson,S. Joy, M. Kochert, R. Lehman, D. Leslie,
R. W. Mannan, R. Reynolds, D. Smith, H. Snyder,
and K. Steenhofforprovidingthoughtfuland construc-
tive reviews of this manuscript. I also thank C. Van
Cleevefor caringforthe nestlingand assistingwith the
photographic record. This material was collecteddur-
inga studyfundedbya challenge-cost-shareagreement
betweenthe University ofArizona and the USDAFor-
estService,SouthwestRegion.Additional fundingwas
provided by Kaibab Industries, the Arizona Wildlife
Federation, and the Arizona Falconer's Association.
LITERATURE CITED
BOAL,C. W., ANDJ. E. BACORN. In press. Siblicide
and cannibalism at Northern Goshawk nests. Auk.
BROWN,L., ANDD. AMADON. 1968. Eagles, hawks
and falcons of the world. Country Life Books, Lon-
don, U.K.
ELLIS,D. H. 1979. Development of behavior in the
Golden Eagle. Wild!. Monogr. 70:1-94.
FYFE, R. W., AND R. R. OLENDORFF. 1976. Mini-
mizing the dangers of nesting studies to raptors and
other sensitive species. Can. Wild!. Servo Occas. Pap.
No. 23.
MORITSCH,M. Q. 1983a. Photographic guide for ag-
ing nestling Prairie Falcons. USDI Bur. Land Man-
age., Boise, ID.
MORITSCH,M. Q. 1983b. Photographic guide for ag-
ing nestling Red-tailed Hawks. USDI Bur. Land
Manage., Boise, ID.
MORITSCH,M. Q. 1985. Photographic guide for aging
nestling Ferruginous Hawks. USDI Bur. Land Man-
age., Boise, ID.
-
FIGURE 8 (top left). Goshawk at 36-38 days post-hatching. Morphological Characteristics: Nestling bodies
are approximately 90% feathered, but downy areas remain along the side of the neck, in the thighs, and in the
underwing covert area. Usually a tuft of down remains just above the cere on the otherwise feathered head.
Rectrices are approximately 3f4full length. Behavioral Characteristics: All nestlings will be branching and some
of the males may fledge from the nest tree. Nestlings/fledglings will fight aggressively over food at the nest but
will still accept being fed by the adult female. Nestlings/fledglings will food beg for long periods.
FIGURE 9 (bottom left). Goshawk at greater than 40 days post-hatching. Morphological Characteristics: Nest-
lings/fledglings appear fully feathered, but downy areas persist along underwing covets. This is only visible when
the wings are spread. The crop will also appear downy when the bird is gorged. Rectrices are still slightly short
of full length. Behavioral Characteristics: Males should be fledged and females will usually fledge by 42 days
old. Fledglings can often be located when they food beg from different locations in the nest stand. At about 45
days the adults will begin providing food at locations away from the nest.
t
40
STUDIES IN AVIAN BIOLOGY
NO. 16
Moss, D. 1979. Growth of nestling Sparrowhawks
(Accipiter nisus). J. Zool., Lond. 187:297-314.
NEWTON,t. 1979. Population ecology ofraptors. Bu-
teo Books, Vermillion, SD.
NEWTON,I. 1986. The Sparrowhawk. T&AD Poyser
Ltd., Staffordshire, U.K.
REYNOLDS,R. T., ANDH. M. WIGHT. 1978. Distri-
bution, density, and productivity of accipiter hawks
breeding in Oregon. Wilson Bull. 90:182-196.
SCHNELL,J. H. 1958. Nesting behavior and food hab-
its of goshawks in the Sierra Nevada of California.
Condor 60:377-403.
STEENHOF,K. 1987. Assessing raptor reproductive
success and productivity. Pp. 157-170 in B. A. Giron
Pendleton, B. A. Millsap, K. W. Cline, and D. M.
Bird (eds.), Raptor management techniques manual.
Natl. Wildl. Fed. Sci. Tech. Ser. No. 10.
YOUNG,L. S., ANDM. N. KOCHERT. 1987. Marking
techniques. Pp. 125-156 in B. A. Giron Pendleton,
B. A. Millsap, K. W. Cline, and D. M. Bird (eds.),
Raptor managementtechniquesmanual.Natl. Wildl.
Fed. Sci. Tech. Ser.No. 10.
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The breeding ecology of the Red-tailed Black Cockatoo Calyptorhynchus banksii escondidus was studied in the northern wheatbelt of Western Australia from the austral spring of 1974 to the end of 1981. The usual clutch was one egg, but 8 of 465 clutches were of two eggs, none of which produced two fledglings. The incubation period was 29 days, similar to that of other species of black cockatoo with similar body mass. The nestling period was 80–84 days, nearly 17% longer than the similarly-sized Carnaby’s Cockatoo C. latirostris. The ages of nestling Red-tailed Black Cockatoos may be estimated by comparison with photographs taken of nestlings of known age or estimated more precisely from the length of the nestling’s folded wing. Aging nestlings enables the calculation of laying and hatching dates.
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... Observations from a series of 7 050 images, taken between 1 November 2016 and 4 January 2017 are described here. Author did not name the species chick was already a 'brancher', that is, it had left the nest, but remained in the nest tree (sensu Boal 1994) and it still returned to the nest to be fed. The goose arrived during daylight on all five visits, with the hooded vulture juvenile arriving at least an hour (mean = 128 min; n = 4) after the goose had left on four days (and not arriving at all on 11 November 2016). ...
A review of the use of birds’ nests by Egyptian geese, including a breeding attempt in a hooded vulture nest
Article
Egyptian geese Alopochen aegyptiaca are widely reported to be territorial and aggressive. They are known to attack and sometimes kill other birds and they may attempt to usurp their nests. Here information is collated on the bird species whose nests have been used or usurped by Egyptian geese. Also presented are observations from a series of camera trap images of an Egyptian goose laying eggs and incubating in a hooded vulture Necrosyrtes monachus nest to which a juvenile hooded vulture returned repeatedly for food. Ten aggressive encounters were recorded between the Egyptian goose and the hooded vultures; the goose prevailed in five of these encounters, the vultures in four and on one occasion both vultures and goose fled the nest. This is the first time that an Egyptian goose has been recorded breeding in a hooded vulture nest. The hooded vulture chick successfully fledged and although the goose incubated for at least 20 days, for reasons unknown, its breeding attempt ultimately failed.
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... We collected measurements only once during the nestling period. Nestling age was determined on the basis of known dates of hatching (when available) and a photographic guide developed by Boal (1994). When possible, nestling sex was determined using size measurements because the sexes are size dimorphic. ...
Effects of Supplemental Food on Parental-Care Strategies and Juvenile Survival of Northern Goshawks
Article
Full-text available
  • Apr 2001
Using food supplementation, we tested whether food limits juvenile survival in a population of Northern Goshawks (Accipiter gentilis) in northeastern Utah. The influence of additional food on female nest attendance also was investigated because those strategies may influence predation mortality rates of juveniles. We provided supplemental food near 13 nests from close to hatching until close to independence during the 1996 and 1997 breeding seasons. Thirteen additional nests served as controls and received no supplemental food. We compared the following variables at treatment and control nests: (1) adult female mass, (2) nestling mass and size, (3) female nest attendance, and (4) juvenile survival. Following supplemental feeding, adult females from treatment nests were heavier than their control counterparts, and remained closer to the nest during the latter part of the nestling period and throughout the postfledging period. Nestlings from supplemented nests were significantly heavier than those from unsupplemented nests, but results for size measurements were equivocal. Survival rates for treatment nestlings were significantly higher than controls in 1997, but not in 1996. Those results support the hypothesis that food does not limit avian reproductive success on an annual basis. Most deaths in 1997 were the result of starvation or sibling competition. That observation, and the fact that fed nestlings were heavier, is consistent with the idea that treatment nestlings were in improved nutritional condition. Overall patterns of mass and nest-attendance for adult female goshawks supports the hypothesis that female condition and behavior are adjusted in response to food supplies. However, it is less clear what role the females' presence in the nest stand plays in mediating juvenile deaths, because we did not document predation as a primary mortality factor during the two years of this study. The apparent flexibility in female nest attendance behavior suggests that such plasticity may be an adaptation to lower the risk of predation.
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... Brood size was considered the maximum number of nestlings counted in a nest regardless of nestling age. I estimated hatch dates by backdating from an estimate of nestling ages based on Meng (1951) and an adaptation of Boal (1994). For the purposes of the analyses presented, I considered nestlings that survived to 25 days of age (80% of first flight age) as fledglings (Steenhof and Kochert 1982). ...
Nonrandom Mating and Productivity of Adult and Subadult Cooper's Hawks
Article
  • May 2001
Among 90 independent pairings of Cooper's Hawks (Accipiter cooperii) in Tucson, Arizona, fewer adult-subadult pairings and more adult-adult and subadult-subadult pairings occurred than was expected. On average, hatching occurred at nests of adult pairs five days earlier than subadult male-adult female pairs, 12 days earlier than adult male-subadult female pairs, and 19 days earlier than subadult pairs. Brood sizes were largest among adult pairs, lower among mixed-age pairs, and smallest among subadult pairs. Adult female Cooper's Hawks nested earlier and had larger broods than subadult females, but brood size did not differ between subadult females paired with adult or subadult males. Adult pairs fledged significantly more young per year than mixed-age and subadult pairs. Differences in phenology between adult and subadult Cooper's Hawks may be associated with adults being preferred as mates. Differences in productivity, however, may be more closely associated with age-related constraints on reproductive physiology of females.
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... Preen oil concentrations of POPs, therefore, correlate well with plasma concentrations, which was previously found in studies on different bird species (Van den Brink, 1997;Yamashita et al., 2007). Goshawks practice preening motions from two weeks of age and preening begins at three weeks of age (Boal, 1994), resulting in a thin layer of preen oil coating their feathers. Lipophilic compounds can thereby end up on the feather surface while preening, providing yet another avian-specific pathway for excretion of environmental pollutants (Gutiérrez et al., 1998;Solheim et al., 2016). ...
Integrated exposure assessment of northern goshawk (Accipiter gentilis) nestlings to legacy and emerging organic pollutants using non-destructive samples
Article
Full-text available
  • Aug 2019
In the present study, concentrations of legacy and emerging contaminants were determined in three non-destructive matrices (plasma, preen oil and body feathers) of northern goshawk (Accipiter gentilis) nestlings. Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs), together with emerging pollutants, including per- and polyfluorinated alkyl substances (PFASs), novel brominated flame retardants (NBFRs), phosphorus flame retardants (PFRs) and Dechlorane Plus isomers (DPs) were targeted. Plasma, preen oil and feather samples were collected from 61 goshawk nestlings in Norway (Trøndelag and Troms) in 2015 and 2016, and pollutant concentrations were compared between the three matrices. In plasma, PFASs were detected in the highest concentrations, ranging between 1.37 and 36.0 ng/mL, which suggests that the nestlings were recently and continuously exposed to these emerging contaminants, likely through dietary input. In preen oil, OCPs (169-3560 ng/g) showed the highest concentrations among the investigated compounds, consistent with their high lipophilicity. PFRs (2.60-314 ng/g) were the dominant compounds in feathers and are thought to originate mainly from external deposition, as they were not detected in the other two matrices. NBFRs and DPs were generally not detected in the nestlings, suggesting low presence of these emerging contaminants in their environment and/or low absorption. Strong and significant correlations between matrices were found for all POPs (rs = 0.46-0.95, p < 0.001), except for hexachlorobenzene (HCB, rs = 0.20, p = 0.13). Correlations for PFASs were less conclusive: linear perfluorooctane sulfonate (PFOS), perfluoroundecanoate (PFUnA), perfluorododecanoate (PFDoA) and perfluorotetradecanoate (PFTeA) showed strong and significant correlations between plasma and feathers (rs = 0.42-0.72, p < 0.02), however no correlation was found for perfluorohexane sulfonate (PFHxS), perfluorononanoate (PFNA) and perfluorotridecanoate (PFTriA) (rs = 0.05-0.33, p = 0.09-0.85). A lack of consistency between the PFAS compounds (contrary to POPs), and between studies, prevents concluding on the suitability of the investigated matrices for PFAS biomonitoring.
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Ashley NF Northern Goshawk Nest Inventory and Monitoring Report -2020
Technical Report
Full-text available
  • Oct 2020
Synopsis of 25 year Norther Goshawk nest monitoring study on the Ashley National Forest, Utah.
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Variation in the Stable-Hydrogen Isotope Composition of Northern Goshawk Feathers: Relevance to the Study of Migratory Origins
Article
Full-text available
  • Aug 2005
The analysis of stable-hydrogen isotope ratios in feathers (δDf) allows researchers to investigate avian movements and distributions to an extent never before possible. Nonetheless, natural variation in δDf is poorly understood and, in particular, its implications for predictive models based on stable-hydrogen isotopes remain unclear. We employed hierarchical linear modeling to explore multiple levels of variation in the stable-hydrogen isotope composition of Northern Goshawk (Accipiter gentilis) feathers. We examined (1) inter-individual variation among goshawks from the same nest, and (2) intra-individual variation between multiple feathers from the same individual. Additionally, we assessed the importance of several factors (e.g., geographic location, climate, age, and sex characteristics) in explaining variation in δDf. Variation among individuals was nearly eight times the magnitude of variation within an individual, although age differences explained most of this inter-individual variation. In contrast, most variation in δD values between multiple feathers from an individual remained unexplained. Additionally, we suggest temporal patterns of δD in precipitation (δDp) as a potential explanation for the geographic variability in age-related differences that has precluded the description of movement patterns of adult raptors using δDf. Furthermore, intra-individual variability necessitates consistency in feather selection and careful interpretation of δDf-based models incorporating multiple feather types. Finally, although useful for describing the movements of groups of individuals, we suggest that variability inherent to environmental and intra-individual patterns of δDp and δDf, respectively, precludes the use of stable-hydrogen isotopes to describe movements of individual birds. Variación en la Composición de Isótopos Estables de Hidrógeno de las Plumas de Accipiter gentilis: Relevancia para los Estudios sobre el Origen de la Migración Resumen. El análisis de los cocientes de isótopos estables de hidrógeno presentes en las plumas (δDf) permite a los investigadores estudiar los movimientos y distribuciones de las aves en un grado nunca antes posible. Sin embargo, la variación natural en δDf es poco entendida, y particularmente sus implicaciones sobre modelos que hacen predicciones con base en isótopos estables de hidrógeno aún permanecen poco claras. Empleamos un modelo lineal jerárquico para explorar múltiples niveles de variación en la composición de isótopos estables de hidrógeno en las plumas de Accipiter gentiles. Examinamos (1) la variación entre individuos de un mismo nido y (2) la variación entre varias plumas de un mismo individuo. Además, determinamos la importancia de varios factores (e.g., aislamiento geográfico, clima, edad y características sexuales) para explicar las variaciones en δDf. La variación entre individuos fue casi ocho veces mayor que la variación en un mismo individuo, aunque diferencias en la edad explicaron la mayoría de esta variación entre individuos. De manera contrastante, la mayor parte de la variación en los valores de δD entre varias plumas de un mismo individuo permaneció inexplicada. Además, sugerimos patrones temporales de δD en la precipitación (δDp) como una posible explicación para la variabilidad geográfica en las diferencias relacionadas con la edad que han imposibilitado la descripción de los patrones de movimiento de aves rapaces adultas utilizando δDf. Asimismo, la variabilidad intra-individual requiere que exista coherencia en la selección de plumas y una interpretación cuidadosa de los modelos basados en δDf que incorporen múltiples tipos de plumas. Finalmente, a pesar de ser útiles para describir los movimientos de grupos de individuos, sugerimos que la variabilidad inherente al ambiente y los patrones intra-individuos de δDp y δDf, respectivamente, impiden el uso de isótopos estables de hidrógeno para describir los movimientos de aves individuales.
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Distribution, density, and productivity of Accipiter hawks breeding in Oregon
Article
Full-text available
Density of nests and productivity of Sharp-shinned Hawks (Accipiter striatus), Cooper's Hawks (A. cooperii), and Goshawks (A. gent&s) within Oregon are of interest because of recent declines of accipiter hawks in the east- ern United States (Schriver 1969, Hackman and Henny 1971, Henny and Wight 1972). One factor implicated in this decline was contamination with chlorinated hydrocarbons (Ratcliffe 1970, Cade et al. 1971, Anderson and Hickey 1972, Wiemeyer and Porter 1970). Snyder et al. (1973) presented data on levels of DDE in eggs of accipiter hawks from various regions in North America, including Oregon. Their data indicated that eggs of each species are contaminated, but they were unable to evaluate the effects of contamination on populations in Oregon as historical data on the abundance of breeding accipiters did not exist. This paper presents information on the distribution of nests, nesting density, and nesting success of Sharp-shinned Hawks, Cooper's Hawks, and Goshawks in Oregon. In an attempt to assess current production trends, nesting densities and productivities of Oregon accipiters are compared to densities and pro- ductivities of accipiters elsewhere in North America and, where appropriate, in Europe.
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Nesting Behavior and Food Habits of Goshawks in the Sierra Nevada of California
Article
  • Nov 1958
Thesis (M.A. in Zoology)--University of California, Berkeley, Sept. 1957. Includes bibliographical references (leaves 78-82). Microfilm. s
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  • Jan 1979
  • T Newton
NEWTON, t. 1979. Population ecology ofraptors. Buteo Books, Vermillion, SD.
Steenhoffor providing thoughtfuland constructhe USDA Forest Service, SouthwestRegion. Additional funding was provided by Kaibab Industries, the Arizona Wildlife Federation, and the Arizona Falconer's Association
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to B. Baker, B. Bibles, E. Bibles, R. Brown, M. Collins,N. Karnovsky, R. W. Mannan, and E.Steadman for assistingwith nest observations.I thank J. Dawson, S. Joy, M. Kochert, R. Lehman, D. Leslie, R. W. Mannan, R. Reynolds, D. Smith, H. Snyder, and K. Steenhoffor providing thoughtfuland constructhe USDA Forest Service, SouthwestRegion. Additional funding was provided by Kaibab Industries, the Arizona Wildlife Federation, and the Arizona Falconer's Association. LITERATURE CITED BOAL,C. W., ANDJ. E. BACORN. In press. Siblicide and cannibalism at Northern Goshawk nests. Auk. BROWN,L., AND D. AMADON. 1968. Eagles, hawks and falcons of the world. Country Life Books, London, U.K.
Development of behavior in the Golden Eagle
  • Jan 1979
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ELLIS,D. H. 1979. Development of behavior in the Golden Eagle. Wild!. Monogr. 70:1-94.
Minimizing the dangers of nesting studies to raptors and other sensitive species
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FYFE, R. W., AND R. R. OLENDORFF. 1976. Minimizing the dangers of nesting studies to raptors and other sensitive species. Can. Wild!. Servo Occas. Pap. No. 23.
The Sparrowhawk. T &AD Poyser Ltd
  • Jan 1986
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NEWTON,I. 1986. The Sparrowhawk. T &AD Poyser Ltd., Staffordshire, U.K.
Assessing raptor reproductive success and productivity
  • Jan 1987
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STEENHOF, K. 1987. Assessing raptor reproductive success and productivity. Pp. 157-170 in B. A. Giron Pendleton, B. A. Millsap, K. W. Cline, and D. M. Bird (eds.), Raptor management techniques manual. Natl. Wildl. Fed. Sci. Tech. Ser. No. 10. YOUNG,L. S., ANDM. N. KOCHERT. 1987. Marking techniques. Pp. 125-156 in B. A. Giron Pendleton, B. A. Millsap, K. W. Cline, and D. M. Bird (eds.), Raptor managementtechniquesmanual. Natl. Wildl. Fed. Sci. Tech. Ser.No. 10.