Winter
1982
ABSTRACTS
ECOLOGICAL
WINTERING
Abstracts
OF THESES
AND
ENERGETICS
BALD EAGLES
137
DISSERTATIONS
AND
FORAGING
BEHAVIOR
OF
The ecological
energetics
andforagingecologyof winteringBald Eagles(Haliaeetus
leucocephalus)
werestudiedfor 2 yearson the NooksakRiverin northwestern
Washington andin the laboratoryat Utah StateUniversity.During 36 food consumption
trials,
daily consumption
by 4 winter-acclimatized
eagleswas 92.0 g/kg on a chumsalmon
(Oncorhynchus
keta)diet, 74.8 g/kg on a black-tailedlackrabbit(Lepuscalifornicus)
diet,and65.1g/kg ona mallardduck(Anasplatyrhynchos)
diet whichwasinverselyre-
latedto thewet energycontents
(0.90,1.22,and1.96kcal/g)of the diets,respectively.
Daily consumption
for combineddietswas88.4 g/kg at -10 C, 75.5 g/kg at 5 C, and
68.0 g/kg at 20 C. Daily grossenergyintake, existencemetabolism,and excretory
energyfor combineddietswere 116.9,94.3, 22.5 kcal/kg at -10 C, 101.8,81.8, and20.0
kcal/kgat 5 C, and89.7,69.1,and20.6 kcal/kg at 20 C, respectively.
Basalmetabolic
rate, asdeterminedby oxygenconsumption,
was2.771 kcal/g/hr with a lower critical
temperatureat 10.6 C and a thermalconductance
of 0.083 cal/g/hr - C. Artificiallyproduced
rain in the laboratorycaused9 and21 percentincreases
in energymetabolism
at rainfalllevelsof 6.1 and22.2 cm/hr, respectively;
however,naturalrain levelsin the
PacificNorthwestwere estimatedto inducea negligibleincreasein metabolism.
Deep
bodytemperatures
of 2 free-livingeagles,measured
with ingestedtransmitters,
were higestduringflight, intermediateduringdiurnalperching,and lowestduringnocturnal
roosting.
Thisnocturnaldepression
alloweda 5 percentenergysavingsof total metabolic heatproduction.
Ambienttemperature,wind velocity,long-waveradiation,and rainfall datafrom3 meteorological
stations
wereusedasinputto the equivalentblack-body
temperature
modelto determineheat productionof free-livingeagles.Daily metabolic
heatproduction
variedbetween383 and426 kcalfor a 4.5 kg eagledepending
on habitat selectionand time of day. By roostingin coniferoushabitat rather than deciduous
habitat,eaglesexperienced
a 6% reductidnin total heat production.
Energysavings
wereattributedto milderwind speed,ambienttemperature,
and long-waveradiation
conditions
foundin coniferous
roosts.
Flightactivity,asmonitored
for 4 radio-tagged
eagles
for38 days,involvedonlyI percentof the24-hourdayandcomprised
only6%of
thedailyenergybudget.The dailyenergybudget(totalenergymetabolized)
for a wild
4.5kg Nooksack
eaglewas407keal/dayanddailyenergyconsumption
(totalenergyrequirement)
was494 keal/day;thesevalueswere approximately
10%greaterthanexistencemetabolism
andgrossenergyintakeof captiveeagles,respectively.
Daily consumptionof 500, 364, or 296 g of chumsalmon,black-tailedjackrabbits,or mallard
ducks,respectively,
is neededby a wild eagleto meetdailyenergyrequirements.
Intraspecifie
interactions
whileeatingsalmon
ontheNooksack
Riverwereunusually
high
with kleptoparasitism
beingthe primarymeansby whicheaglesprocuredfood.Adult
eagleswere dominantoveryoungerbirdsand were moresuccessful
at stealingfood.
Juvenilesand subadults
had low feedingefficienciesand consumed410 and 459
g/bird/dayof salmon,respectively,
on an artificialfeedingstationwhichwaslessthan
the 552 g/bird/dayingested
by adults.Youngeaglesthusfailedto procurethe needed
500g/bird/day.Theeffectsof thissocially-mediated
fooddeprivation
onyoungeagles
,ranged
fromsuboptimization
of thetimebudgetto possible
starvation.
Analyses
of the
138
RAPTOR RESEARCH
Vol. 16, No. 4
factorsaffectingwinterenergybudgetsindicatethat BaldEaglesexhibitphysiological
andbehavioraltraitswhichmaximizeenergy-exploitation
efficiencyandminimizeneedlessenergydrains.Protectivemanagement
effortsshouldbe directedat reducingenergy
stress
therebyincreasing
overwintersurvival.
Stalmaster,
MarkVictor.1981.Ecological
energetics
andforaging
behavior
ofwintering
BaldEagles.
Ph.D.Dissertation.
UtahStateUniversity,
Logan.157pp.
BOOK
REVIEWS
Hailer, H. 1982. Raumorganisation
und Dynamik einer Populationdes Steinadler
Aquila chrysaetos
in den Zentralalpen.
Ornithologische
Beobachter,
79:163-211.Germanwith Englishsummary
andcaptions
for tablesandmaps.
Importantlong-termstudyof a populationof GoldenEaglesthat isbelievedat saturationlevel,nowthathumanpersecution
hasstopped.
Concludes
thatrateof production
is
controlled
by pressure
fromfledgedimmatures
andnon-breeding
adults.Productivityis
between.4 to .6 fledgedeagletsper pair annually,whereasit can be twice that in a
sparser,
recoveringpopulation.
Dean Amadon
ANNOUNCEMENTS:
THANK
1982 ANNUAL
YOU TO LOCAL
COMMITTEE
RRF MEETING
AND ALL PARTICIPANTS
We thankthe followingpeople,from the local committee,for all their time and
energydonated
in planningandcoordinating
the 1982annualRRFmeetingin SaltLake
City,Utah:James
Gessaman,
AlbertHeggen,OwenHogle,RonaldJoseph,
CarlMarti,J.
R. Murphy,KathySmith,James
Ure,StellanieUre,PhillipWagner,andC. M. White.
We thankall thosestudents
fromUtahStateUniversity
andBrighamYoungUniversitywhohelpedin somanyways.We are alsogratefulto thosewho chairedsessions,
andmostimportantly,
we are thankfulto thosewhosharedtheirdatawith usthrough
thepaperstheypresented.
All of theseworkingtogether
madefor a successful
annualmeeting.