Unusual Fishing Behavior of the Eurasian Sparrowhawk ( Accipiter nisus )

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LETTER
J. Raptor Res. 52(1):000–000
Ó2018 The Raptor Research Foundation, Inc.
UNUSUAL FISHING BEHAVIOR OF THE EURASIAN SPARROWHAWK (ACCIPITER NISUS)
BE
´LA MESTER
1
Hungarian Academy of Sciences, Centre for Ecological Research, Danube Research Institute, Department of Tisza River
Research, 4026 Debrecen, Bem te´r 18/c, Hungary
THOMAS OLIVER ME
´R}
O
Nature Protection and Study Society—NATURA, Milana Raki´
ca 20, 25000 Sombor, Serbia
KEY WORDS:Eurasian Sparrowhawk; Accipiter nisus; behavior;
fishing;predation;urban;winter.
The Eurasian Sparrowhawk (Accipiter nisus; hereafter
sparrowhawk) is a generalist predator (Quinn and Cress-
well 2004), feeding primarily on birds (over 90% of prey
items in most studies; Newton 1986, Zawadzka and
Zawadzki 2001, Bujoczek and Ciach 2009). Sparrowhawks
occur frequently in human-altered landscapes, including
residential areas, where some individuals overwinter (e.g.,
McGrady 1991, Me´r}o and Z
ˇuljevi´c 2010). Hunting success
can be higher at low temperatures, and lower when
precipitation is present and the wind is strong (Hilton et
al. 1999, Quinn and Cresswell 2004). Under unfavorable
conditions, sparrowhawks can alternatively consume other
small prey, such as small mammals (Tomeˇsek and ˇ
Cerma´k
2009). We here report on unusual prey selection and
hunting behavior of the sparrowhawk.
Our observation took place in Debrecen (462 km
2
), the
third largest city in Hungary, where the sparrowhawk is one
of the most common raptors (Bozsko and Juha´sz 1985).
During a walk in the Botanical Garden of the University of
Debrecen (47833.490N, 21837.290E, 126 masl) on 18 January
2017, we spotted a subadult (2 yr old; SY) sparrowhawk
engaged in several short, quick, low flights above the non-
frozen part of a koi (Cyprinus carpio haematopterus) pond
(water garden). These apparent predation attempts on koi
usually started with hovering flight similar to that of the
Eurasian Kestrel (Falco tinnunculus), followed by quick,
sharp turns as if in pursuit of a fish, followed by immersion
of the sparrowhawk’s feet into the water (Fig. 1). Each
predation attempt took up to several seconds. Resting time
between predation attempts lasted about 3 min while the
sparrowhawk stood on the edge of the ice, intently watching
the water. The bird always rested on the opposite side of the
previous resting point. While the sparrowhawk was ‘‘fish-
ing,’’ we approached from 20 m to 4 m so that wecould take
better photographs. Although the sparrowhawk noticed us
immediately, it continued its activity, and made a total of 15
unsuccessful attempts before being disturbed by a man
walking near the pond. To our knowledge, no such fishing
behavior has previously been reported for the sparrow-
hawk.
The part of the koi pond where this sparrowhawk
attempted to fish was not frozen because of a water
circulation system in constant operation, and perhaps
because of feeding activity of Mallards (Anas platyrhynchos).
Our observation started at 0950 H and lasted until 1045 H.
The weather was clear and sunny with mild gusts of wind;
the temperature was 18C and the relative humidity was
61% (both measured at 2 m above the ground). The
average daily temperature had been consistently below 08C
since mid-December, and the average depth of snow cover
had been approximately 4 cm since late December.
We suggest three possible explanations for the fishing
behavior of this sparrowhawk. First, the most common fish
species in the koi pond were goldfish (Carassius auratus
auratus) and koi. Swimming slowly near the surface, white,
orange, or red koi may appear to be easy prey. Aquarists
have reported that avian predators such as herons and
kingfishers easily catch koi or goldfish (Stickley 1990). The
garish coloration and slow swimming of koi and goldfish
near the surface might have attracted the sparrowhawk. A
second possible explanation might be the prolonged
presence of snow cover that year. Our previous experience
observing and trapping sparrowhawks suggests that avian
prey may more easily detect a hunting sparrowhawk against
a white background (snow cover) than against other
background colors. This may reduce hunting success in
winter, prompting sparrowhawks to hunt alternative prey. A
third explanation may be related to the age of the observed
sparrowhawk. Prey such as the slowly swimming, garishly
colored koi may trigger innovative hunting attempts among
subadult and inexperienced, but motivated individuals.
1
Email address: mester.bela@okologia.mta.hu
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Potential previous, but possibly irreproducible success in
catching fish might have encouraged this Sparrowhawk to
attempt to ‘‘fish’’ again.
These hypotheses are not mutually exclusive, and all
three may be related to the unfavorable winter conditions.
Generally, in the northern hemisphere the mortality of
raptors increases during winter due to starvation or risky
hunting in unfavorable conditions (Roth et al. 2005).
Mortality of inexperienced subadult birds in particular is
highest during their first winter (Lahti et al. 1998). For
sparrowhawks, subadult mortality, from fledging through
the following April, can be as high as 70% (Newton et. al
1982, Newton 1986). Risky (e.g., attacking bats in caves;
Bereczky 2011) or innovative hunting (this study) may
result from food stress due to unfavorable weather
conditions or a prey deficit in winter (Newton 1986). In
conclusion, our observation suggests that raptors may be
able to adopt unusual hunting or foraging behavior and
prey selection in response to changing environmental
conditions, and changing availability of potential prey
resources.
We thank Michael Smart and two anonymous reviewers
for help preparing this report. Financial support was
provided to BM by the ´
UNKP-17-3 ‘‘New National
Excellence Program of the Ministry of Human Capacities’’
grant. Photographic equipment was provided by the
Olympus Test & Wow in cooperation with Tenno Foto Kft.
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Figure 1. From top left to bottom right: a sparrowhawk resting on ice at the edge of a koi pond, hovering flight over the
water, attacking underwater prey, and in flight exiting the water. (Photos by Be´ la Mester)
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Received 30 April 2017; accepted 16 August 2017
Associate Editor: James F. Dwyer
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