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Behaviour of the white stork Ciconia ciconia: a review

Authors:
Behaviour of the White Stork Ciconia ciconia:
a review
Marcin Bocheński & Leszek Jerzak
Institute of Biotechnology & Environmental Protection, University of Zielona Góra,
Prof. Z. Szafrana 1, PL-65-516 Zielona Góra, Poland, e-mail: M.Bochenski@ibos.uz.zgora.pl,
L.Jerzak@ibos.uz.zgora.pl
ABSTRACT:The aim of this paper is to review the current knowledge about the White Stork
behavioural system and to give a basic description of the known White Storks’ behaviours.
Also some comments, new interpretations and conclusions, supported by our observations
in Kłopot colony (Western Poland), are given. At the same time, we would like to point out
problems, appearing when one wants to interpret some of the White Stork behaviours, as
well as to indicate the areas of knowledge, where more detailed studies are necessary to im-
prove our understanding of White Stork ecology and evolution.
KEY WORDS:White Stork, behaviour, ethology, review
Introduction
The species of birds are so numerous and their behaviors are so diverse, that to
gain even a moderate understanding of the behaviour of a handful of species is an
enormous task. The description and classification of behaviour is in any case an es-
sential preliminary to any analysis (Hinde 1973). However we may expect many
papers describing of behavior of many common birds’ species, surprisingly these
are not that many. The next step is to describe the detailed ethogram which is a cat-
alogued description of the discrete, species-typical patterns that form the basic be-
havioral repertoire of the species (Martin & Bateson 1988). This ethogram makes
it possible to study behaviour and to compare these data from throughout the spe-
cies distribution.
The White Stork is a well known, charismatic and usually beloved bird. The his-
tory of White Stork studies is long-standing and the scientific literature is ample.
Some of the articles deal with the White Stork behaviour, but surprisingly, this
item is relatively poorly documented.
Tryjanowski P., Sparks T.H. & Jerzak L. (eds.)
The White Stork in Poland: studies in biology, ecology and conservation
Bogucki Wydawnictwo Naukowe, Poznań 2006
Not every aspect of the White Stork’s behavioural system was studied equally
well. On the one hand, many papers were issued about Stork’s food, feeding behav-
iour and ecology (e.g. Pinowski et al. 1986, 1991, Skov 1989, Carrascal et al. 1990,
Alonso et al. 1991, Struwe & Thomsen 1991, Böhning-Gaese 1992, Dziewiaty
1992, Thomsen & Struwe 1994, Lakeberg 1995, Bogucki & Ożgo 1999, Löhmer &
Harms 1999, Groner & Ayal 2001, Moritzi et al. 2001, Antczak et al. 2002,
Barbraud et al. 2002, Tryjanowski & Kuźniak 2002,). On the other hand, only a few
advanced studies focused on the behavioural features connected with colonial
breeding of the White Storks (Carrascal et al. 1990, Tortosa & Redondo 1992a,
1992b, Sasvari et al. 1999a, Blas et al. 2005, Kasprzak et al. 2006).
Since the first half of the 20th Century, knowledge has been gathered from a
small and restricted breeding population of the White Stork in Southern Africa. A
few descriptions indicate that the breeding behaviour of these birds is similar to
the European breeders (Broekhuysen 1965, 1974). Furthermore, a small number
of papers concern the White Stork’s behaviour on the wintering grounds. In sev-
eral papers dealing with other topics, questions about breeding behaviour are only
scarcely discussed, and if they are, only as general remarks (e.g. Pennycuick 1972,
Creutz 1988, Van den Bossche et al. 2002, Brouwer et al. 2003).
Additional papers deal with research on captive birds. Recently, some advanced
laboratory research aimed at connecting the biochemistry, haematology and some
behavioural aspects of the White Stork. Results of these studies usually corre-
spond to the research in the wild, and moreover, supplement them and shed new
light on the evolutionary aspects of the White Stork’s behaviour (Löhr 1961,
Broekhuysen 1974, Hall et al. 1987, Mata et al. 2001, Michard-Picamelot 2002,
Blas 2005, Kasprzak et al. 2006).
Since 2003, a new type of behavioural studies on the White Stork has been in
progress in a colony in the small village of Kłopot (Western Poland). The investiga-
tions are mainly concentrated on time budgets, breeding and feeding behaviours in
the context of high population densities. Some laboratory studies (in aspects of
biochemistry, haematology, contaminationetc.) are included as well, with the first
papers being only recently issued (Jerzak et al. 2006, Kasprzak et al. 2006).
The aim of this paper is to review our current knowledge about the White Stork
behavioural system and to give the basic description of the known White Storks’
behaviours. Also some comments, new interpretations and conclusions, sup-
ported by observations in the Kłopot colony, aregiven. At the same time, we would
like to point out problems appearing when one wants to interpret some of the
White Stork behaviours, as well as to indicate the areas of knowledge, where more
detailed studies are necessary to improve our understanding of White Stork ecol-
ogy and evolution. Below we describe the 8 main categories of behaviour.
Part I. Study species and general behaviour
The White Stork is sometimes solitary but basically is a gregarious species. Storks
frequently breed in single, segregated pairs, but in some parts of their range, they
form loose colonies of dozens or even hundreds of pairs. On the feeding grounds,
296 Marcin Bocheński & Leszek Jerzak
they gather large flocks, both during the breeding season and wintertime. Breeding
pairs are monogamous, and the nest and its nearest surroundings comprise the
fiercely defended territory.
Typical types of behaviour and displays were defined and described by Kahl
(1972). These are given below.
The best known behaviour and, at the same time, the most common way of
intraspecific communication of the White Stork is the Up-Down Display with Bill Clat-
tering. The display can be performed with slight modifications, depending on the sit-
uation and the intended meaning. It is almost exclusively performed on the nest.
In general, the Stork first leans forward with the bill pointed downwards; then,
it stretches the neck rapidly up and backwards, finally touching its back with its
crown. The display ends by slowly bending the head and neck to the initial point,
with the bill held down with some pecking at the nest material. This sequence can
be repeated a number of times. During this performance, the bird stands on one or
two feet or slowly steps in place. Nevertheless, the display can also be made while
lying, or sitting on the tarsi on the nest. During this display, Storks almost always
clatter with their bill in a characteristic way. It is a mechanical sound, produced by
fast knocking the mandibles together. The clattering starts when the neck and head
are thrown backwards and continues until the display is finished (Phot. 1).
In the presence of a raptor or a strange stork near the nest, a special modifica-
tion of Up-Down Display is performed. Threat Up-Down Display with Wing Pumping re-
sembles typical display, but usually is preceded by the only true throat voice – hiss-
Behaviour of the White Stork Ciconia ciconia: a review 297
Phot. 1. Pair during threat up-down display against intruder stork (phot. Grzegorz Jędro)
ing. Then, after throwing head on the back, stork extends the neck and bill toward
the intruder clattering all the time and cocking the tail very strongly. During this
performance the stork, especially the male, partially open its wings and rhythmi-
cally “pumps” them up and down (Phot. 2). If the intruder is still in vicinity of nest
or approaches to it, this display may turn to another – Forward Threat Display. Here
the stork manifests its aggressive behaviour by keeping the body in a horizontal
line, retracting the neck, orienting bill toward the opponent and stepping from one
leg to another. Also the feathers of neck and upper back are erects (Phot. 3). When
intruder attempts to alight on the nest, Nest Covering Display may be performed.
The stork bends its legs, opens and drops its wings, and covers the nest. Also it
may sit or lie down on it with open wings. Often the intruder is chased away by the
defending bird (usually male), which pursues it for up to a few hundreds meters
from the nest with aerial bill clattering (Bauer & Glutz von Blotzheim 1966, Cramp
& Simmons 1977, authors unpubl. data).
When a White Stork is disturbed at the nest (e.g. by a human or domestic ani-
mals) or if a strange stork is approaching but still is far away, it performs Anxiety
Stretch Display. The bird stands in an erect position while compressing the body
plumage, sometimes erecting the neck feathers, and leaning towards the disturb-
ing object. Occasionally, the alarmed Stork utters a single “clap” with the bill while
standing in the Anxiety Stretch. In White Stork colonies, this display seems to func-
tion as a warning signal to other individuals (Kahl 1972, Boettcher-Streim 1992,
authors unpubl. data).
298 Marcin Bocheński & Leszek Jerzak
Phot. 2. A male during threat up-down display with wing pumping and observing the in-
truder (phot. Grzegorz Jędro)
When an unmated or newly mated male is confronted by a female approaching
to the nest, it may perform the Head-Shaking Crouch Display. During this display the
bird crouches on the nest, raises its wings and tail, erects the neck and back feath-
ers and forcefully shakes its head.
Part II. Detailed descriptions
1. Nest occupancy
1.1. Arrivals and occupation of the nest
Usually, males are the first to arrive on the breeding site. Uncommonly, the pair re-
turns from the winter quarters together or on the same day, and very exceptionally,
the female arrives before the male (Creutz 1988, Profus 1991, Radkiewicz 1992,
Tortosa & Redondo 1992a, Barbraudu & Barbraud 1999, Kosicki et al. 2004).
White Storks have got a quite strong nest-bond and site fidelity. Each breeding
season, they tend to return to the same breeding area and preferably to the same
nest as well. Frequently the same individuals may be observed on the same nest in
subsequent years (Löhr 1961, Schüz 1981, Meybohm & Dahms 1975, Meybohm &
Fiedler 1983, authors unpubl. data).
Some studies reveal that Storks coming back to the breeding sites, at first prefer
to occupy the larger nests or the ones that have been occupied continuously or at
least for a long time. Moreover, pairs breeding on these kinds of nests, as a rule
achieve a proportionally high reproductive success. These nests may be favoured as
Behaviour of the White Stork Ciconia ciconia: a review 299
Phot. 3. Threat up-down display (phot. Grzegorz Jędro)
indicators of high quality breeding territories (Tortosa & Redondo 1992a, Sasvari
et al. 1999a, Tryjanowski et al. 2004, Tryjanowski et al. 2005). This hypothesis may
be only partially true and only apply for populations breeding in low densities or
for pairs breeding solitarily. It seems, that it doesn’t hold for Storks breeding colo-
nies, and surely not for the dense ones, where all or most of the nests are situated
in habitats of similar quality. In this case, the pattern of nest occupancy may simply
reflect the strength of nest-bond and the mating system, with the superior quality
of birds returning earlier in the season. This question needs more detailed studies,
connecting nest history and nest occupancy pattern of White Storks (Creutz 1988,
Barbraud et al. 1999, Sasvari et al 1999a, Tryjanowski et al. 2004); (see Mating sys-
tem below).
During spring migration, single as well as paired birds may, probably more of-
ten than expected, stay over in a nest only for a few hours or days, using it as a rest-
ing place. When they alight, they can behave in the same way as on their “breeding
nest”, but after some time they abandon it and continue the passage (Wuczyński
2005).
After alighting on the selected nest, Storks performs the Up-Down Display with
Bill Clattering and often with Wing Pumping. This performance is often repeated, and
the principal intention of this behaviour is to scare off the potential rivals and in-
truders as well as to attract a female. Another behaviour displayed by Storks during
the first hours and days upon arrival, is to (probably) show the occupancy of the
nest by sustained sitting on it. The bird sits or lays in the nest for a long time, as if it
was “waiting” for the mate during a few or even a dozen of hours (Löhr 1961,
Bauer & Glutz von Blotzheim 1966, Cramp & Simmons 1977, Creutz 1988, au-
thors unpubl. data).
Sometimes one individual or a pair of Storks occupy more than one nest, not
only in colonies but also when the nests are more distant. One or more additional
(satellite) nests can be used as a source of nest material for the “breeding nest” or
as a resting and roosting place. In this case it is defended in the same way as is the
“breeding nest”. When a satellite nest is remote from the breeding nest, it is quite
easily taken over by Storks arriving later in the season. As time progresses the
Stork pairs concentrate their activities more and more on the “breeding nest” and
the tendency to defend more than one nest becomes weaker (Haas 1963, Bauer &
Glutz von Blotzheim 1966, authors unpubl. data); (see Nest Defending below).
1.2. Nest building and repairing
When the possession of a nest is secured, individual Storks and later pairs, start in-
tensively to collect the nest material (twigs, sticks, hay, straw, grass, soil, dung),
taking it mainly from the ground (Phot. 4). When a Stork is still unmated or its
mate is absent from the nest, birds look for nest material in the proximity of the
nest. They watch its surroundings carefully and remain ready for immediate return
and defence. After pair formation, both mates bring building material to the nest,
but the contribution of the male is usually higher (Cramp & Simmons 1977,
Creutz 1988, Böhning-Gaese 1992, Tortosa & Redondo 1992a, authors unpubl.
data).
300 Marcin Bocheński & Leszek Jerzak
Behaviour of the White Stork Ciconia ciconia: a review 301
Phot. 4. Pair rearanging nest material (phot. Grzegorz Jędro)
Phot. 5. Parent comming with nest material (phot. Marcin Bocheński)
Many of the birds (both males and females), especially in colonies, try to steal
material from the neighbouring nests. Stealing occurs particularly from occupied
and “active” nests. This behaviour saves time and energy during nest building and
allows more time for guarding the nest (and female). If the resident owners dis-
cover the stealing attempt, they react with immediate defence (see Nest defending
below); (Bauer & Glutz von Blotzheim 1966, Tortosa & Redondo 1992a, authors
unpubl. data).
Nest material is delivered by storks during whole breeding season, up to the
fledgling of young (Phot. 5), to improve the proper nest microclimate for develop-
ing hatchlings, as well as to keep it sanitary and clean in the nest (Schüz 1943b,
Glutz 1966, Creutz 1988, Böhning-Gaese 1992, Tortosa & Villafuerte 1999, au-
thors unpubl. data).
1.3. Nest Defence
An occupied nest and its nearest vicinity becomes a territory, which is hardly de-
fended before the other storks. Isolated breeding pairs may defend area of radius
up to few hundreds meters, while in colonies defence may be only the immediate
surrounding of the nest (roof or tree-branch). In dense colonies, where nests are
situated (e.g. on the roof), one next to another, only the nest site is defended. Thus,
territory size and as a consequence, density of breeding population and frequency
of the antagonistic behaviours, may be influenced by several factors (Creutz 1988,
Tryjanowski & Kuźniak 2002, Kasprzak et al. 2006, authors unpubl. data).
As a rule, the male makes a larger contribution to the nest andterritory defence
than the female. He spends more time guarding the nest in the first stages of
breeding (pairing, incubating and chicks raising) and he forages closer to the nest.
He usually starts the defence displays and the aggressive interactions (e.g. when an
intruder approaches the nest or the nest is attacked); he shows more effort and vio-
lence, especially during the Wing Pumping display (Schüz 1942, Bauer & Glutz von
Blotzheim 1966, Creutz 1988, Tortosa & Redondo 1992a, Redondo et al. 1995,
Ożgo & Bogucki 1999, authors unpubl. data).
Throughout the breeding season, and particularly at the beginning, when
Storks arrive to their nesting sites and occupy the nests, it often results in fights
between the already established birds and the newcomers. These interactions can
occur with a variable intensity and aggression level, ranging from only gestures and
ritual poses (e.g. Threat Up-Down or Forward Stretch Display) to violent, bloody, even
day-long and deadly combats. During sharp fights over the nest, Storks can even di-
rect their aggression towards their own mate, perhaps not recognizing it (Creutz
1988, Profus 1991, authors unpubl. data). The fights with intruders are one of the
main causes of brood loss, either during incubating (up to near 40% of all loses
cases) or chick raising (up to >40% of all loses cases) (Jakubiec 1991, Guziak &
Jakubiec 2006). The reasons for these struggles are not quite clear. Probably the
nest-bond can play a role (see Mating system below)as for instance, when fights are
induced by pairs which return to the nest they occupied in a previous year but are
confronted with other individuals that are already settled. The newcomers defend
this nest as actual “owners”; their defence is the stronger the further the breeding
302 Marcin Bocheński & Leszek Jerzak
season is in progress, when eggs or chicks are already present in the nest. Intruders
can also be the younger, not fully matured birds, which return later from the win-
tering areas, as well as birds that have lost their brood. These birds form loose,
wandering flocks and fly back and forth over the breeding range. At times they also
try to take over already occupied nests, even late in the season, when chicks are al-
ready present (Schüz 1936, 1981, Haas 1963, Bauer & Glutz von Blotzheim 1966,
Profus 1991, authors unpubl. data).
In colonies, the pattern of territory defence differs. At the beginning of the
breeding season when birds first return and establish territories, the Threat
Up-Down Display is performed incessantly whenever a strange Stork (not the
owner” of the nest) flies nearby. After a few days, a defence reaction is triggered
only when neighbouring birds approach the nest too closely or trespass the terri-
tory border. Later still, until the departure for the wintering grounds, aggressive
interactions between neighbours are rare. When on the contrary, a completely un-
familiar Stork appears in the colony, it immediately excites a reaction of the breed-
ing birds. First, they carefully watch the intruder while performing the Anxiety
Stretch Display; when the intruder comes nearer, they show the Threat Up-Down Dis-
play, usually in very agitated way (authors unpubl. data). This indicates that colo-
nially breeding Storks may know and recognize each other, and in the course of
time, learn to respect the territory borders. When young Storks practice their first
flights and approach a strange nest, they usually don’t evoke a defence reaction of
the residents unless they really try to alight on it (see Nestling behaviour below;
Redondo et al. 1995, authors unpubl. data).
When a predator (bird or mammal) approaches the nest, adult birds show the
Forward Threat Display. Throughout their breeding range, White Storks have to fear
only a few predators. The most important are large birds of prey such as the
White-Tailed Eagle Haliaetus albicilla, the Golden Eagle Aquila chrysaetos and
Bonelli’s Eagle Hieraaetus fasciatus. These species are quite often reported to chase
or attack Storks (e.g. Probst & Knötzsch 1975, Schüz 1975, Creutz 1988,
Samusenko 1996, Langgemach & Henne 2001, Van den Bossche et al. 2002,
Jakubiec & Peterson 2005). The presence of raptors in the vicinity of the nest or a
colony nearly always evokes a very strong reaction. The Threat Up-Down with Wing
Pumping and the Forward Threat Displays are performed by both mates on the nest in
a really fierce way, sometimes for several minutes. If a raptor appears during the
absence of one parent, e.g. while it is foraging or resting nearby, it immediately re-
turns to join in his mates’ display (authors unpubl. data). Occasionally the reaction
is so strong, that the Stork mobs and chases the Eagle away (Langgemach, Henne
2001). The appearance of smaller raptor species such as buzzards Buteo sp., kites
Milvus sp., hawks Accipiter sp. or corvids Corvidae sometimes elicits the Anxiety
Stretch Display but more often Storks show no reaction at all (the Threat Up-Down
Display is performed very rarely); (Creutz 1988, authors unpubl. data).
Among ground predators, threats can be from a Fox Vulpes vulpes which hunts
for storks feeding or resting on the ground. In the face of martins Martes sp. or cats
Felis domesticus, which can rob the nest of eggs or small chicks, the storks perform
nest defence or Forward Threat Display, even during the night (Creutz 1988, authors
Behaviour of the White Stork Ciconia ciconia: a review 303
unpubl. data). Occasionally, defence reactions to predators are performed outside
the nest and on the feeding grounds (Kahl 1972).
1.4. Other birds in the White Stork nest
While conspecifics are not tolerated near the nest, Storks are usually indifferent to
other animals not being predators or potential prey. The phenomenon of other bird
species nesting in a White Stork’s nest is well known. The most common co-occu-
pants are Sparrows Passer spp., Starling Sturnus vulgaris, Grey Wagtail Motacilla alba,
Kestrel Falco tinnunculus and several others. These birds find proper spaces to build
their own nest and the presence of a Stork can be of advantage against predators.
White Storks usually tolerate these co-occupants and show no aggression, al-
though some Storks have been observed to catch and consume some of the co-resi-
dents, especially their young, (Creutz 1988, Indykiewicz 1998, Brix 1999,
Bocheński 2005, authors unpubl. data).
2. Pairing and copulations
2.1. Mating system
Although Barbaud and Barbaud (1999) revealed that there is no age related
assortative mating amongst storks, the following facts demonstrate that the pair
usually is formed by birds of similar experience or quality: 1) the male (or less
common female) accepts the first partner which arrives to the nest at the begin-
ning of breeding season; 2) earlier returning birds are older, more experienced,
than younger ones, and 3) there is strong nest-bond influence. Moreover, quite of-
ten the same mates meet together at the same nest for more than one breeding sea-
son (Schüz 1981, Meybohm & Dahms 1975, Meybohm & Fiedler 1983, Creutz
1988, Profus 1991, Radkiewicz 1992, Tortosa & Redondo 1992a, Barbraud &
Barbraud 1999, Barbraud et al. 1999, Sasvari et al. 1999a, 1999b, Sasvari & Hegyi
2001, Kosicki et al. 2004, Tryjanowski et al. 2004.).
2.2. Behaviour towards mate
When after the mating, one of the mates approaches the nest, the other usually
performs the Up-Down Display with Bill Clattering. As a rule, the arriving bird re-
sponds with the same behaviour, sometimes even when it’s still flying. This display
differs from the Threat Up-Down as the bill is not directed towards the mate and the
tail is not cocked so strongly (Phot. 6).
In general, there is not a simple, fixed pattern of performing the Up-Down Dis-
play as a greeting ceremony on the nest. The frequency and intensity of this display
may depend on the stage of breeding, the strength of the pair-bond between mates,
perhaps their earlier acquaintance and even the condition of birds (Kahl 1972, au-
thors unpubl. data).
Storks probably recognise their mates, as well as their neighbours when nesting
in colonies, mostly upon the visible features such as plumage characteristics, size
and shape of the bill, some individual marks (authors unpubl. data). Possibly, the
colour and pattern of the bare skin on the base of lower mandible plays a role in the
mutual recognition, especially amongst breeding partners (Fangrath & Helb 2005).
Nevertheless, the recognizing system requires more detailed, experimental studies.
304 Marcin Bocheński & Leszek Jerzak
Behaviour of the White Stork Ciconia ciconia: a review 305
Phot. 7. Pair during preening (phot. Grzegorz Jędro)
Phot. 6. Greeting ceremony for partner comming with the nest material (phot. Grzegorz
Jędro)
When the pair bond is being established, mates often preen each other during
the time they spend together in the nest (Phot. 7). Females seem to be more in-
tense in inclined to this behaviour (Schüz 1943a, Bauer & Glutz von Blotzheim
1966, Kahl 1972, Cramp & Simmons 1977, Creutz 1988, authors unpubl. data).
2.3. Copulation
Copulation almost exclusively takes place on the nest. It is induced by male and
isn’t preceded by special display. Female seems not to solicit copulation actively,
but by exhibiting a special posture (with back and tail held in a horizontal line,
usually with the head lowered and pecking the nest, as if she was really performing
(or only pretending to) a rearrangement of the nest) she may shows the willing-
ness or acceptance to the copulation. Moreover, this may provoke male to conduct
this act. Usually, directly before this act, the male paces around the female, than
lays his head or neck on the female’s neck or back, slightly pressing her down. Af-
ter that, he climbs on the female’s back, bends his legs to lower his body and initi-
ates cloacal contact. During this courtship, the male preens the female’s neck
feathers with his bill, shaking his head from side to side and uttering a very soft
clattering noise. While copulating, the birds try to keep their balance by partially
opening the wings (Phot. 8). As a rule, the entire copulation lasts for about 10–20
seconds. As before the copulation, there is no special behaviour after the act is
completed. Usually birds start to preen their plumage or rearrange the nest mate-
rial. When a female rejects the male’s attempt, she does so by simply moving away
306 Marcin Bocheński & Leszek Jerzak
Phot. 8. Copulation (phot. Grzegorz Jędro)
(Cramp & Simmons 1977, Kahl 1972, Creutz 1988, Hancock et al. 1992, Tortosa &
Redondo 1992a, authors unpubl. data).
Most of the copulations are performed in a standing position but sometimes a
pair copulates when the female is sitting or lying in the nest. This is the case when
the birds differ greatly in the size or this position may help with cloacal contact
(Schüz 1934, Kahl 1972, authors unpubl. data).
First copulation can take place a few hours or even minutes after female’s arriv-
ing and acceptance (Cramp & Simmons 1977, Creutz 1988). The most intensive
copulations are performed during period of pair formation and the week before be-
ginning of egg lying. Also delivering nest material by males may have an influence
on the copulation pattern. Male bringing the nest material increase the opportu-
nity of copulation by causing female to adopt proper body position, that allows him
to begin pre-copulating behaviour (Tortosa & Redondo 1992a, authors unpubl.
data).
The White Stork belongs to the category of birds with a very high copulation
rate. The average number of copulations reaches to c.a. 160 in the first weeks and
above 200 during the whole breeding season. Usually, most of the copulations are
performed during the morning or evening hours, with a frequency up to 2 times
per hour (Tortosa & Redondo 1992a, authors unpubl. data.).
Sometimes, pairs continue to copulate after egg laying, during incubation or
even later in the breeding season when the chicks are almost flying. Even in August
and just before autumn migration, Storks can still be seen copulating, yet not in the
nest but on the place where the adult birds usually rest, e.g. on a roof nearby or on a
neighbouring platform of an electrical pole (Schüz 1936, Bauer & Glutz von
Blotzheim 1966, Creutz 1988, authors unpubl. data.). The meaning of these copu-
lations is not clear. Perhaps, they play a role in the pair-bonding or function as a re-
laxing behaviour.
2.4. Extra Pair Copulation and bigamy
The pair bond is formed during the first days after the female’s arrival. Neverthe-
less, in this time Extra Pair Copulations (EPC) may be observed. Both pair mem-
bers might engage in EPC which takes place mostly during the partner’s absence at
the nest. EPC is rather rarely performed by Storks, even in dense colonies, where
possibilities for EPC are more plentiful, (less than 1% of all copulations in two
Spanish colonies and only 3 EPC observed during 4 breeding seasons in Kłopot col-
ony). It indicates that the sperm competition in the White Stork may be relatively
weak (Tortosa & Redondo 1992a, authors unpubl. data).
The high copulation rate (see Copulation above) may be connected with the EPC
phenomenon and can be a part of “male assessment” by the female, estimating her
partner’s quality before the breeding starts (Tortosa & Redondo 1992a). This
might explain why some females desert their mates during the period of pair-for-
mation, even after egg laying. Over consecutive years, females change their nests
(and partners) more often than males (Schüz 1934, Haas 1963, Bauer & Glutz von
Blotzheim 1966, Meybohm & Dahms 1975, Meybohm & Fiedler 1983, Tortosa &
Redondo 1992a, authors unpubl. data).
Behaviour of the White Stork Ciconia ciconia: a review 307
Apart of the EPC situation, when one male is bonded with two females on the
one nest, may be observed. It can last only for the first weeks of breeding or even up
to the young fledgling. All three birds can behave like during normal breeding sea-
son: all deliver the nest material, defend the nest, incubate the eggs or feed the
chicks. It is not clear, whether this is true polygyny, where the male fertilizes both
females, or if the second female only plays the role of non-breeding “helper”
(Bauer & Glutz von Blotzheim 1966, Radkiewicz 1986, Assfalg & Schüz 1988,
Schmidt 1989).
3. Eggs lying and incubating
As a rule, females lay an egg every second day. The incubation starts after either the
first or the second egg is laid. Both mates take part in incubation, but the female
contributes more than the male, brooding almost exclusively at nights. The fre-
quency of relief increases in inclement weather conditions (cold or rain), thus the
female can spend more time foraging. While one mate is brooding, the other fre-
quently stands on the nest, guards in the proximity, or flies away for feeding. In col-
onies, birds tend to spend more time guarding their mate than solitary breeding
pairs (Creutz 1998, Hancock et al. 1992, Tortosa & Redondo 1992a, Barbraud &
Barbraud 1999, Sasvari & Hegyi 2001, authors unpubl. data).
4. Chick raising
4.1. Parental care
As a rule, parents of the White Stork are present on the nest, when chicks are
hatching, especially during unfavourable weather conditions. When a hatchling
frees itself from the egg shell, the parents perform the Up-Down Display as a greet-
ing ceremony (Creutz 1988, Tortosa & Villafuerte 1999, authors unpubl. data).
The highest mortality and loses rates occur during first 2–3 weeks of chicks’
life. In this time they need to be warmed and guarded by parents. During first 3–4
weeks after hatching, at least one parent almost always is present in the nest (Phot.
9). Later, chicks are left unattended for a longer period, and when they are ready to
fledge it may last for few hours. Time designated for incubating or guarding young
strongly depends on many factors, e.g. weather conditions, food availability or
density of breeding population (Glutz 1966, Kahl 1972, Creutz 1988, Tortosa &
Villafuerte 1999, Moritzi et al. 2001, Sasvari & Hegyi 2001, Tortosa & Castro 2003,
Jovani & Tella 2004, Kasprzak et al. 2006, authors unpubl. data)
During hot and sunny days, or when it’s raining, Stork parents stand on the
nest above the chicks in the Wing-Drooping Posture – with the wings slightly opened
and primaries fanned downward, as “an umbrella” to shade the brood (Phot. 10).
This is very common behaviour, observed among a wide range of species (Cramp &
Simmons 1977, Creutz 1988, authors unpubl. data).
4.2. Feeding young
The young storks are fed by both parents, which deliver the food in their stomach
or crop and then regurgitate it on to nest’s floor (Phot. 11). The regurgitation act
takes place almost exclusively on the nest, even when fledglings are able to fly
308 Marcin Bocheński & Leszek Jerzak
Behaviour of the White Stork Ciconia ciconia: a review 309
Phot. 10. Parent shadowing the chicks (phot. Grzegorz Jędro)
Phot. 9. Parent and the chick (phot. Grzegorz Jędro)
(Creutz 1988, authors unpubl. data). Nevertheless, accidentally, feeding can have
the place on the ground (Broekhuysen 1965).
As a rule, male brings a greater total amount of food than female. It may be the
result of it’s better hunting success or effectiveness as well as fact that male often
forage closer to the nest then female (Lakeberg 1995, Ożgo & Bogucki 1999,
Sasvari & Hegyi 2001). The frequency of feeding and the amount of delivered food
is strongly connected with the time budget of the breeding pair during the season
and can depend on many factors as breeding stage, brood size, breeding density,
richness of food sources, weather conditions or the age and experience of the par-
ents. On average, a breeding pair can perform up to 16 feeding actions per day
(Creutz 1988, Lakeberg 1995, Sasvari et al. 1999a, Sasvari & Hegyi 2001, Kasprzak
et al. 2006, authors unpubl. data).
Food delivery to the nest can take a place also during light, clear nights, when
storks are able to forage (Glutz 1966, Hancock et al. 1992, Jerzak et al 2006, au-
thors unpubl. data).
During hot summer days parents deliver water to the chicks, usually after feed-
ing them. The main purpose of providing water is to support thermo-regulation.
Parents cool their chicks by showering the water brought in the bill and throat
(Schuz 1943a, Glutz 1966, Creutz 1988, authors unpubl. data.).
The frequency and amount of delivered food decrease by the end of chick rear-
ing and adults forage intensively for enlarging fat reserves prior to migration . Sim-
ilar behaviour has been noted in captive birds and probably is regulated by hor-
310 Marcin Bocheński & Leszek Jerzak
Phot. 11. Parent regurgitating food itiems (phot. Marcin Bocheński)
mones (Hall et al. 1987, Tortosa & Redondo 1992a, Mata et al. 2001,
Michard-Picamelot el al. 2002, Sasvari & Hegyi 2001, Van den Bossche et al. 2002,
authors unpubl. data).
4.3. Parental infanticide
Among White Storks parental infanticide is quite commonly observed. Adult
throw away from the nest their own eggs or chicks (either alive or dead) and if
hatchlings are still small parents swallow or try to devour them. This phenomenon
is called “Kronism”. As a rule, the smallest and the least developed chick is killed.
Due to asynchronous hatching, it is usually the youngest sibling (Schüz 1936,
1957, 1984, Borowski 1963, Meybohm, Fiedler 1983, Creutz 1988, Tortosa and
Redondo 1992b, Hartung 2001, Jerzak, Wąsicki 2005, authors unpubl. data). This
event is common and can be the reason of more than 40 % of all loses during egg
laying and incubation and more than 70% of all brood loses during chicks rearing
(Jakubiec 1991, Guziak, Jakubiec 2006). The motives for this behaviour are not
clear enough. The gender, age and experience of stork parents seems not to matter.
Parental infanticide is probably the way, in which the parents actively reduce their
brood, adjusting the number of chicks to the actual feeding conditions and their
own ability to rear young (and thus increasing the quality of the surviving chick). It
in turn may be connected with changing weather conditions. But still, we don’t
know about the influence of parental infanticide on the sex ratio between the
brood and potential costs of rearing young of different gender. Due to fact that this
phenomenon is highly discreet and difficult to observe, studies based on genetic
analysis should be included (Szidat 1935, Schüz 1936, 1943b, 1957, 1984, Creutz
1988, Tortosa & Redondo 1992b, Sasvari et al. 1999b, Zieliński 2002).
5. Behaviour of the nestling
5.1. Begging Display
Similar to adult birds, the young storks may recognize their parents by plumage
features as well as colour and pattern of the bare skin on the base of their mandible
(Fangrath & Helb 2005).
Small, 2 days old chicks already perform Up-Down Display with Bill Clattering as a
greeting of parent. At the beginning the display is soft and quiet, but when the
chick grows older, it becomes louder and stronger (Kahl 1972, Creutz 1988, au-
thors unpubl. data).
As soon as a parent alights on the nest, the chicks perform the Begging Display,
which starts the first day of life. They sit on their tarsi, lean forward, cock the tail
and partially spread the wings. They intensively peck at the parent’s bill and some-
times even try to thrust their own bill into their parent’s throat. At the same time
they slightly pump the wings and perform a quiet hissing (Phot. 12). Also they can
peck at the nest material. This behaviour is a signal for the adult bird to regurgitate
(Glutz 1966, Kahl 1972, Cramp & Simmons 1977, authors unpubl. data.).
Behaviour of the White Stork Ciconia ciconia: a review 311
5.2. Sibling competition
Siblings mutually compete for food. This competition looks like a “race for food”,
when chicks try to catch and swallow the largest amount of regurgitated food. Due
to the asynchronous hatching, the oldest chick, especially during the first weeks of
life, profits from his age lead and comes by the most (Sasvari et al. 1999b).
Hostility between siblings usually isn’t harmful and is observed amongst the
older chicks (Schüz 1984, Torotsa & Redondo 1992, Redondo et al. 1995). The ag-
gression intensifies when less food is delivered. Similarly, the competition be-
comes more frequent as the young grow older, and the oldest chick inflicts the
most vigourous “attacks” (Redondo et al. 1995, Sasvari et al. 1999b). The level of
aggression may also be connected with and regulated by hormonal levels (e.g. tes-
tosterone) (Sasvari et al. 1999b, but see also Ros et al. 2001, Blas et al. 2005). Nev-
ertheless, these aggressive behaviours don’t affect the chick’s mortality and do not
influence on the storks’ breeding success.
Siblings usually tolerate each other, do not fight, and often preen one another.
During the flight training period, when young Storks practice their first flights, the
fledglings that stayed behind occasionally defend the nest against their own sib-
lings and prevent them from alighting, probably due to misrecognition (Tortosa et
al. 1995, Brix 1999, authors unpubl. data). Play behaviour between older siblings
can look aggressive and exceptionally it can even turn into real harmful and dan-
gerous behaviour, causing wounds or even death (Phot. 13) (Schüz 1985).
312 Marcin Bocheński & Leszek Jerzak
Phot. 12. Chick begging during feeding action (phot. Marcin Bocheński)
During flight training in colonies, practising young Storks sometimes try to
alight on a nest other than their own (Phot. 14). In that case, they are usually
chased away by the adult nest-owners or their chicks. Occasionally they succeed to
land despite of residents’ attacks and then often fall into “akinesis” (see Behaviour
against threat below). As the attack frequency decreases, the foster chick can be
treated as a “legitimate” sibling. Sometimes, it is allowed to feed together with the
resident young (Schuz 1943a, Bauer & Glutz von Blotzheim 1966, Redondo et al.
1995, authors unpubl. data). This behaviour can benefit the “adopted” young be-
cause in the foster nest it can obtain a larger food portion since the aggression of
the foster siblings is weaker than in the natal nest (Redondo et al. 1995).
5.3. Reaction to threats
When faced with intruders or predators, young Storks show two types of reaction.
The most common behaviour is “akinesis”: the bird lies motionless on the nest
floor, has eyes wide open or covered by the third eyelid (nictitating membrane),
mimicking being dead (Phot. 15). Akinesis is performed by chicks in the age of 20,
up to 50 days old. After that age, young more often try to escape from the nest or
show overt aggression. The most vigorous and aggressive individuals even attack
the intruder. Occasionally, chicks start pecking at the nest material in order to
frighten the intruder (Schüz 1943b, 1985, Glutz 1966, Boettcher-Streim 1992, au-
thors unpubl. data).
Behaviour of the White Stork Ciconia ciconia: a review 313
Phot. 13. Fledgelings during play near the nest (phot. Grzegorz Jędro)
314 Marcin Bocheński & Leszek Jerzak
Phot. 15. Chicks presenting akinesis (phot. Marcin Bocheński)
Phot. 14. Young storks learning to fly (phot. Marcin Bocheński)
6. Foraging behaviour
6.1. Hunting methods
White Storks use many different hunting strategies and methods. The most com-
mon are lurking for and gathering prey.
Lurking for the prey – mainly for the vertebrate animals (voles, mice, moles or
other animals up to size of young hare). The Stork stands still next to the ani-
mal burrow, with lowered head, beak pointed downwards, looking and waiting
for the appearance of prey. Although this method is rather time-consuming and
not quite efficient, it provides the largest food (and energy) intake. It is often
used by non-breeding birds and by breeding pairs, when their chicks are develo-
ped enough to swallow relatively large prey items (Struwe & Thomsen 1991,
Böhning-Gaese 1992, Dziewiaty 1992, Löhmer, Harms 1999, Antczak et al.
2001, Good 2004).
Collecting the prey – mainly the invertebrates (e.g. snails, earthworms, beetles,
etc.). The Stork slowly walks across the meadow or field and picks small ani-
mals from the ground or plants. This method is applied in the early period of
chick rearing or by young Storks after fledgling. It is also used during agricultu-
ral works, when Storks follow the machines. Collecting allow storks to achieve
a high catching efficiency, but is not energetically profitable (Bauer and Glutz
von Blotzheim 1966, Pinowski et al. 1991, Struwe & Thomsen 1991, Böhn-
ing-Gaese 1992, Dziewiaty 1992, Löhmer & Harms 1999).
Other, but infrequently used methods are:
catching prey within water (similarly to herons), both fresh and salt (ponds, la-
kes, rivers), mainly fish, but also water invertebrates (e.g. crayfishes, snails)
(Dziewiaty 1992, Böhme 2002);
tactolocation: the Stork probes with the opened bill into water or mud and sear-
ches for prey like Spoonbills (Löhr 1961, Bauer & Glutz von Blotzheim 1966,
Kahl 1972);
aerial catching – White Storks are perfectly able to catch small flying birds (e.g.
sparrows Passer ssp.) or insects (e.g. beetles Scarabidae); (Berthold 2004, Jerzak
et al. 2006);
storks can perform catching swimming birds (e.g. ducklings) from the water
surface (Bashta 1995).
White Storks readily take advantage of agricultural works on arable fields and
meadows (harvesting, ploughing, mowing), as well as of hay and fallow fires,
where they catch flushed or injured prey (Pinowski et al. 1986, 1991, Creutz 1988,
Pfeifer 1989, Skov 1989, Struwe & Thomsen 1991, Thomsen & Struwe 1994, au-
thors unpubl. data).
As a rule, White Storks maximise food intake by selecting the feeding site and
strategy that brings about the most abundant and/or the most energetically efficient.
Nevertheless, the foraging behaviour is modified by many factors, e.g.: age and expe-
rience of bird, breeding status, age of brood or prey availability (Sackl 1987, Skov
1989, Carrascal et al. 1990, Alonso et al. 1991, Böhning-Gaese 1992, Groner & Ayal
2001, Antczak et al. 2002, Barbraud et al. 2002, Van den Bossche 2002).
Behaviour of the White Stork Ciconia ciconia: a review 315
6.2. Territorial behaviours on feeding grounds and flock foraging
Pairs nesting in lower densities usually react aggressively towards conspecifics on
the feeding grounds. The behaviour is similar to that on the nest, with perfor-
mance of Forward Threat Display with Wing Pumping, Head-Shaking Display as well as
chasing the intruder away. Also pecking and wing-hitting may occur. The aggres-
sive interactions have an influence on the time spent on the feeding ground and
hunting efficiency (Dziewiaty 1992, Lakeberg 1995, Löhmer, Harms 1999).
Storks breeding in higher densities or in colonies tend to forage in flocks
(Phot. 16). This brings some benefits, e.g.: indication of feeding habitat quality, in-
creasing the foraging efficiency, reduction of costs of nest guarding. But the costs
of it may be the higher competition about food sources (Carrascal et al 1990,
Kasprzak et al. 2006, authors unpubl. data).
White Storks can forage from dawn to dusk, but they are most active in early
morning and evening hours, especially on hot summer days (Creutz 1998, authors
unpubl. data). This pattern is observed among migrating and wintering birds as
well (Van den Bossche et al. 2002, Brouwer et al. 2003). Foraging can also take
place during light, moonlit nights or next to an artificial light source (Creutz 1988,
Lakeberg 1995, Jerzak et al. 2006, authors unpubl. data).
6.3. Behaviour in face of other birds on the feeding ground
Territorial behaviour of White Storks on the feeding grounds also can be performed
against other species. Sometimes, especially solitary breeding storks chase away
316 Marcin Bocheński & Leszek Jerzak
Phot. 16. Foraging flock on the meadows (phot. Grzegorz Jędro)
individuals of Black Stork Ciconia nigra, Grey Herons Ardea cinerea, Crane Grus grus,
Lapwing Vanellus vanellus or even some birds of prey (Lakeberg 1995, F. Aritzi –
pers. comm.)
7. Behaviour during migration and wintering
The behaviour of White Storks at the end of the breeding season and during migra-
tion is strongly connected with the type of flight they are using (soaring in ther-
mals and then gliding high above the surface) (Creutz 1988). Full-grown young ca-
pable to start migration, abandon their nests a few days before the parents do so.
The adult birds depart somewhat later, in synchrony. This way, the families do not
migrate together (Cramp & Simmons 1977, Creutz 1988, Profus 1991, Van den
Bossche et al. 2002, Kosicki et al. 2004). Birds gather in meadows, pastures or ara-
ble fields, where they forage intensively and then fly together to the roosts. Thus,
the more migration is in progress, the more the flocks enlarge (see Van den
Bossche et al. 2002). During migration, this gathering tendency is also observed
also in captive birds (Hall et al. 1987).
White Storks migrating in huge flocks benefit from some advantages. It reduces
the costs of migration by increasing the possibility of finding good thermals, which
allow storks to maximize the efficiency of flight. A large flock is also more skilful in
optimizing flight speed, compensating the influence of the wind and reducing the
deviations from the proper migration direction (Pennycuick 1972, Liechti et al.
1996). (This behaviour is performed also on the breeding grounds, when storks are
forced to look for food far away from the nesting place; authors unpubl. data)
Roaming in groups may be profitable for the young inexperienced birds, which
take advantage in migrating together with more experienced individuals by learn-
ing the fly ways and good feeding sites, and thereby reducing risks and danger
(Liechti et al. 1996, Chernetsov et al. 2004). On the other hand, following an adult
more experienced birds can be disadvantageous. Young birds are usually in poorer
condition and less efficient in food searching. So it may be detrimental or impossi-
ble to adjust their speed to the faster movements of the older birds (Van den
Bossche et al. 2002).
During migration, White Storks may also use thermals produced by artificial in-
stallations as chimneys and stacks. It can allow them to migrate even during the
night (Bramley 1979).
When White Storks are soaring or gliding together with birds of prey (e.g. ea-
gles Aquila sp., kites Milvus sp. or buzzards Buteo sp.), especially during migration,
they usually show no antagonistic behaviour (e.g. Brix 1998, authors unpubl.
data).
The knowledge about White Stork behaviour during wintertime is explicitly
poor. In the wintering areas in the Sahel zone, White Storks are most active during
morning and evening hours, feeding on arable fields, fallows or open shrublands.
They forage in huge flocks, mainly on locust swarms. The hottest part of day is
spent in rest, near water pools or in wetlands (Van den Bossche et al. 2002,
Brouwer et al. 2003).
Behaviour of the White Stork Ciconia ciconia: a review 317
8. Other behaviours
8.1. Resting and roosting
Breeding White Storks rest and roost in the nest or its nearest vicinity. The time de-
voted to this behaviour depends on few factors, e.g. the brood stage, numbers and
age of chicks, availability of food, presence of other storks in the nest surrounding
and on the feeding grounds (Glutz 1966, Böhning-Gaese 1992, Lakeberg 1995,
Kasprzak et al. 2006, authors unpubl. data).
The place where storks rest and roost, depends on the stage of brood. During
the first parts of breeding season both birds rest and roost on the nest. Later, when
chicks are bigger, one parent (the most often female) stays on the nest, while the
second stands nearby on some elevated perch (on the roof, tree branch or electrical
pole). When chicks are larger and almost fledging, both parents usually rest and
roost outside the nest, in its proximity, but still guarding the nest and brood (Phot.
17) (Cramp, Simmons 1977, Creutz 1988, authors unpubl. data).
The nest is also used for roosting a few days after fledging. Young storks, which
are able to fly, spend the day foraging in the surroundings of the nest but return in
the evening and sleep in the nest (Creutz 1988, authors unpubl. data).
Non-breeding Storks, as well as migrating and wintering birds tend to roost
communally. They select safe sites, where many individuals can find a perch: trees,
roofs or water pools. Very rarely White Storks are observed roosting in open areas
as e.g. arable fields or meadows (Creutz 1988, Van den Bossche et al. 2002, authors
unpubl. data).
8.2. Thermoregulatory behaviours
When ambient temperature is low (e.g. during night, in the morning or when
standing in the water), resting storks often stand on one leg and the bill hidden in
the ruffed neck feathers, keeping the body warm and not allowing it to radiate
through the legs (Phot. 18). When the ambient temperature is high and the sun is
intensively shining, storks defecate the excrements on their legs, increasing the en-
ergy loss from the blood by evaporation and perhaps reflection of the sun off their
white legs. This behaviour (called urohydrosis) is observed both in the breeding
range and the wintering areas, and among either: adult and young storks (Bauer &
Glutz von Blotzheim 1966, Kahl 1972, Prinziger, Hund 1982, Schulz 1987, authors
unpubl. data). Also exhaling with widely open bill and deeply breathing allows
cooling of the blood and loss of energy to the ambient via evaporation.
Acknowledgements
We would like to thank prof. Chuck H. Trost, dr. Józef Radkiewicz, prof. Dieter
Wallschlaeger, dr. Krista Dziewiaty, Kai-Michael Thomsen and Kuba Kosicki for
their help in access to some references. To an anonymous reviewer we are obliged
for their critical and useful comments to the first versions of text. Also we express
gratitude to Grzegorz Jędro (White Stork Museum in Kłopot) for improving text
with pictures presenting some White Stork behaviours. Special thanks to dr. Gert
Baeyens for improving English and first comments to the text.
318 Marcin Bocheński & Leszek Jerzak
Behaviour of the White Stork Ciconia ciconia: a review 319
Phot. 18. Resting adult stork (phot. Marcin Bocheński)
Phot. 17. Resting pair of storks (phot. Marcin Bocheński)
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324 Marcin Bocheński & Leszek Jerzak
... The stork parent is indeed in average constantly pointing toward the center of the nest. Once the chicks are old enough, not only do the parents leave them more often alone in the nest (Bochenski andJerzak 2006, Duquet 2018) but I observe that when in the nest, they no longer orient toward the center. The change in behavior from the parents has been identified between the 36 th and 40 th day of the chicks, while in the literature, this change is observed around the 45 th day after hatching (Tortosa and Castro 2003, Tsachalidis et al. 2005, Duquet 2018). ...
... The change in behavior from the parents has been identified between the 36 th and 40 th day of the chicks, while in the literature, this change is observed around the 45 th day after hatching (Tortosa and Castro 2003, Tsachalidis et al. 2005, Duquet 2018). The 45 th day corresponds to the maximum of weight of the chicks but this limit can vary with weather conditions and food availability (Bochenski and Jerzak 2006). A way to identify nests with chicks past their maximum of weight could therefore be to look at the direction of the guarding parent and see whether it faces the center of the nest or not. ...
... The dependence however in the time to the zenith supports that the prime reason for the stork to orient is a balance between shadowing the brood and keeping its eyes protected from too much sun exposition. For shade provision, storks also use a wing-drooping posture, which enlarges their shadow while maintaining a safeguarding position (Bochenski and Jerzak 2006). With this, I conjecture that the orientation is chosen on sunny days from the sun direction and from its intensity or height in the sky, which proxy is the hour as it finds its maximum at the zenith, with the parent favoring wing-drooping posture and alignment to the sun when the latter would be too intense. ...
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Video-monitoring has become in the last decades common practice for animal observation and conservation purposes. In Ornithology, it is mostly used for tracking predators and nest surveillance, but, with the rapid development and spreading of webcams on nests for educational purposes, new opportunities arise for behavioral investigation, through citizen science for instance. In this article, we use video-monitoring from a public webcam on a White stork ( Ciconia ciconia ) nest and perform systematic image analysis to record the positioning and orientation of the guarding parent on the nest, during the nestling period over 60 days. From this data of 450 orientation samples, correlations with weather parameters are drawn. Our results suggest that the sun is responsible for most of the orientation with an hourly dependence, while the wind has prevalence during rainy days. A change in the parent behavior is also observed around the time the nestlings are known to attain their maximal weight. These preliminary findings provide new insights on weather influence on parental care behavior likely linked with the parent's sensing. The versatility of the proposed method allows for behavioral studies on a wide variety of species.
... This comprised: (i) 27 (73 %) resident, including five endemic or near endemic, species, (ii) ten migratory species, and (iii) five globally threatened species, including the vulnerable Tawny Eagle Aquila rapax and Eastern Imperial Eagle Aquila heliaca, and the near-threatened Rouget's Rail Rougetius rougetii, Pallid Harrier Circus macrourus and Abyssinian Longclaw Macronyx flavicollis (BirdLife International 2021; Appendix A). Although previous reports (e.g., Bocheński & Jerzak 2006, Sanchez-Zapata et al. 2007, Fashing et al. 2010 show that a wide variety of bird species may prey upon Desert Locusts, our observations comprise the first records of foraging on locusts for 12 species: Wattled Ibis Bostrychia carunculata, Rouget's Rail, Alpine Chat Cercomela sordida, Rüppell's Robin-chat Cossypha semirufa, Mountain Thrush Turdus plebejus, Ethiopian Thrush Psophocichla simensis, Abyssinian Ground Thrush Zoothera piagiae, Red-breasted Wheatear Oenathe bottae, Thekla's Lark Galerida malabarica, Abyssinian Longclaw, Abyssinian Slaty Flycatcher Melaenornis chocolatina and Red-billed Chough Pyrrhocorax pyrrhocorax. We noted two major types of foraging strategies used by the birds: aerial and ground. ...
... They are known to feed on Desert Locusts on their wintering grounds, such as in the Sahel zone, and sometimes follow such swarms during their migration (Bocheński & Jerzak 2006). However, we have never encountered such large-sized flocks at BMNP during 20 years of observations in the park. ...
... Orthopterans, as well as a variety of other above-ground, plant-living invertebrates, are highly vulnerable to machinery-caused mortality or injury during mowing (Humbert et al., 2010a(Humbert et al., , 2010b, and these insects are very quickly picked up by the storks (Alonso et al., 1991;Orłowski et al., 2019). When hunting on meadows being mown, the storks simply follow the mowing machines, picking up prey items as they go; the catching efficiency in this case is high (Bocheński and Jerzak, 2006). ...
Article
The intensification of farm management practices on grasslands has reduced the abundance of many species of animals. Mowing, a procedure essential to the continuing existence of farmland meadows, inevitably causes mortality among the animals inhabiting them, especially invertebrates, and exposes sites where white storks Ciconia ciconia can forage conveniently and more efficiently. We studied the foraging activities of storks on meadows being mown and compared these with the birds’ foraging patterns on unmown meadows and meadows cleared of hay in the extensively managed farming landscape of east-central Poland. Foraging success was deemed to be the capture of a prey item as manifested by the stork raising its head and swallowing prey item. The storks’ foraging success on meadows being mown was roughly the same as on unmown meadows but was significantly lower than on those cleared of hay. The number of steps taken by storks – a measure of the energy they expended on foraging – was far higher on meadows being mown than on unmown ones. Even so, on meadows being mown, storks caught proportionately more vertebrates (voles) (5.2% of all prey items) than on cleared meadows (1.4%) and unmown meadows (0.2%). The fact that vertebrates are considerably energy-richer than invertebrates was probably the main reason why storks were attracted to forage on meadows being mown, even though their foraging efficiency was not particularly high – an aspect emphasised in the literature. The sequential (asynchronous) mowing of the highly fragmented, semi-natural meadows in this part of Poland coincides with the time when storks are feeding their young. This is probably a key aspect governing the high density of this species.
... Droughts and rainfalls in the African wintering quarters (Kanyamibwa et al. 1990;Kania 2006), weather conditions in the breeding areas in early spring and during the early nestling period (Kosicki 2012;Tobolka et al. 2018), mortality during migration (Schulz 1988;van den Bossche et al. 2002), habitat alterations associated with agricultural intensity (Johst et al. 2001;Janiszewski et al. 2014), industrialization and other anthropogenic influences -are all external factors known to shape stork's population dynamics. Moreover, the strong density-dependence of the white stork (Saether et al. 2006;Gadenne et al. 2014) also links population fluctuations with intra-specific factors, for instance age structure and competitive interactions, both affecting their productivity (Bocheński & Jerzak 2006;Kosicki & Kuźniak 2006). Data from various parts of the species range indicate that slower changes in abundance concern core areas, with dense populations, while smaller and unsaturated populations, subjected to the Allee effect, are characterized by the greater amplitude of changes in a short time (Schimkat 2004;Kaatz et al. 2017). ...
Article
Full-text available
Although white stork Ciconia ciconia counts go back to the XIX century, making the species a model in population investigations, substantial gaps remain in the knowledge of its large-scale population dynamics. In particular, incomplete past estimates from the core breeding areas leave the long-term changes uncertain. In this paper, we provide the earliest estimation of population size and spatial distribution of the white stork in its main stronghold (Poland) to reconstruct the species long-term trends. Based on original survey data collected during the 2nd (1958, incomplete in Poland) and 3rd (1974, successful) International White Stork Census (IWSC) we compared stork numbers in a random sample of villages surveyed on both occasions. We applied linear models to estimate the population growth rate between 1958 and 1974 and to assess spatial variation in population change across the country. Finally, we collated worldwide stork numbers obtained from all IWSCs and discuss the long-term population trends in light of new data. The stork population in Poland in 1958 was estimated at 46,100 breeding pairs and the nationwide density at 14.7 pairs/100 km². A strong decline (by 30.2%, 1.88% per year) was noted between 1958 and 1974 across Poland with prominent spatial variation reflecting differences in local densities. The strongest declines in absolute terms affected the most abundant populations in Eastern Poland. Our data show that in the mid-20th century, the stork population in Poland was close to the current level, but it experienced a massive decline during the 1960s–1980s. This decline was consistent with trends in the worldwide and regional European populations, contrary to earlier statements indicating limited, if any, changes in the core European area. Overall, our data expand knowledge on the long-term dynamics in the white stork numbers and show that even massive changes may easily go undetected if based on non-solid data.
... Water transfer from adults to nestlings occurs among several bird species under warm weather and sun exposure, when adults bring and regurgitate water in the mouth or over the body of the young. This behavior helps the thermoregulation and prevents dehydration of nestlings, and is displayed by birds as diverse as cormorants, storks, shoebills, and passerines (Kahl 1973;Buxton et al. 1978;King and Chastant 1982;Bocheński and Jerzak 2006; D'Angelo and Sazima 2019). ...
Article
Food transfer (allofeeding) is part of courtship and bonding behaviors of several bird species in varied families worldwide. Bonding behavior among parrots and other birds includes mutual preening and food transfer. Herein, I report on water transfer (allodrinking) in a couple of Rainbow Lorikeets Trichoglossus moluccanus in a mangrove at urban Sydney, Australia. The couple drank water accumulated in a mangrove branch hole, after which the male preened the female’s nape. Then, the couple interlocked their bills crosswise and bobbed their heads slightly. The birds disconnected briefly, the female with a liquid layer over the tongue including the brush tip. The couple resumed bill interlocking, a large drop visible under the male’s tongue. As the crosswise bill movements proceeded, the male showed a drop within the bill and the female has a liquid layer over the bill edge. Only liquid transfer was noticed, no food particles. Rainbow Lorikeets feed mostly on nectar and pollen and mate for life, and I expect that lorikeets allofeed with nectar transfer while bonding. I suggest that the same applies to water transfer between the couple, and hypothesize on the situation suitable for the derivation of water sharing from courtship feeding.
... Fights with intruders are the cause of the greatest brood losses at the stages of incubation and raising young (approx. 40%) (Bocheński & Jerzak, 2006). At the same time, the nests that are most intensively covered with excrement may be the most attractive (see Sergio et al., 2011). ...
Article
Finding a good breeding site, especially for those bird species that build large nests, is a crucial element in the settlement of a new potential area. Understanding the site selection process is not only interesting from an ecological theoretical point of view, but also has strong conservation implications. How do birds assess the quality of a site? How can we manipulate that process to encourage the settlement of birds at a particular site? In this study, we tested experimentally how whitewashing (liming with a mixture of mainly calcium oxide and water) relocated and newly located nests of white stork Ciconia ciconia affected their occupancy pattern. Whitewashing significantly improved re-occupancy of previously occupied nests in the year after relocation by about 20%, with no loss in productivity. However, there was a lower occupation rate for relocated nests at long-abandoned sites, and limited occupation of nests in novel locations. Whitewashing has a very long local tradition, and is not only commonly accepted, but also supported, by farmers.
... The White Stork's nest is one of the largest and heaviest structures built by birds worldwide (Cramp and Simmons, 1998;del Hoyo et al., 2020): it can reach over 1.8 m in height, a diameter of over 2.0 m and a weight exceeding 1000 kg (Schimkat et al., 2017). White Storks are long-lived birds and have a strong nest-bond and site fidelity, so they may use their nest for many years in succession (Bocheński and Jerzak, 2005). ...
Article
The physiological and behavioural activities of animals have far-reaching impacts on the characteristics and functioning of soil. This includes vertebrates, which are capable of modifying the physicochemical and biochemical properties of soil. To date, however, no species is known to be responsible for the entire process of soil formation, modification and maintenance. Large-bodied birds build nests which they then use for several years or even decades. During nest construction or renovation, birds gather and transport to the nesting site organic and mineral matter that includes tree branches of various sizes, twigs, turf, straw and hay. Over time, during subsequent breeding events, adult birds supply further loads of organic matter to the nest, such as food remains, excrement, pellets, feathers, egg shells and other materials. Taking the White Stork Ciconia ciconia as an example, we have shown that the materials deposited in the nests of large-bodied birds gradually produce ornithogenic soils over the years, with distinguishable layers having different physicochemical characteristics and biochemical activities. The tested nesting substrate met the criteria for ornithogenic material; the layers had appropriate thickness and phosphorus pentoxide (P2O5) content. Results of the study indicates that the material contained in White Stork nests have the characteristics of Histosols. Moreover, such nests harbour assemblages of fungi and arthropods that contain species typical of soil mycobiota and fauna, respectively. This study is the first to describe a soil that is formed, modified and maintained entirely by vertebrates and is physically isolated from the ground. Our results highlight the fact that the nests of large birds are unique structures in ecosystems and provide a habitat for a rich and diverse assemblage of organisms.
... In the surroundings of Madrid, parakeets build their nests associated with nests occupied by breeding white storks. Despite parakeets can steal nest material from conspecific neighbours [16,42], we have never recorded cases of parakeets stealing sticks -to storks, may be due to of differences in the size and ductility of building materials for each species. Although nesting site availability does not explain the use of stork nests, as monk parakeets may use a variety of nesting substrates [65,95], this association may confer breeding advantages to parakeets [23]. ...
Article
Full-text available
Background: Non-native species are often introduced in cities, where they take advantage of microclimatic conditions, resources provided by humans, and competitor/predator release to establish and proliferate. However, native communities in the surrounding rural or natural areas usually halt their spread through biotic resistance, mainly via top-down regulative processes (predation pressure). Here, we show an unusual commensal interaction between exotic and native bird species that favours the spread of the former from urban to rural habitats. Results: We show how Monk parakeets Myiopsitta monachus, an invasive species often introduced in cities worldwide, associated for breeding with a much larger, native species (the white stork Ciconia ciconia) to reduce predation risk in central Spain, thus allowing their colonization of rural areas. Parakeets selected stork nests close to conspecifics and where breeding raptors were less abundant. Parakeets always flushed when raptors approached their nests when breeding alone, but stayed at their nests when breeding in association with storks. Moreover, when storks abandoned a nest, parakeets abandoned it in the following year, suggesting that storks actually confer protection against predators. Conclusions: Our results show how a protective-nesting association between invasive and native species can counteract biotic resistance to allow the spread of an invasive species across non-urban habitats, where they may become crop pests. Monk parakeet populations are now growing exponentially in several cities in several Mediterranean countries, where they coexist with white storks. Therefore, management plans should consider this risk of spread into rural areas and favour native predators as potential biological controllers.
... During the ringing process we collected blood samples for molecular sexing and took photos of feet perpendicularly to the ground. Chicks were easy to catch, as they are characterized by akinesis and do not attempt to escape during visits to the nest (Bocheński & Jerzak 2006). ...
Article
Capsule: There were no statistically significant differences in digit ratio between male and female chicks of the White Stork Ciconia ciconia. Aims: To test the hypothesis that the ratio of digit lengths was related to sex in White Stork nestlings, and to explore the relationship between digit ratio and other biometrics. Methods: We examined 101 White Stork chicks from a breeding population in western Poland. We measured the second, third and fourth digits from the left and right feet, took measurements of several body parameters (lengths of the bill and wing, body mass), and sexed all nestlings using molecular genetic methods. Results: Males were characterized by having significantly longer digits than females, however, we found no sexual dimorphism in any digit ratio in White Stork chicks. Nor did we find any relationship between digit ratio and body condition measurements. Conclusion: Our results confirm the hypothesis that sexual dimorphism for digit ratio does not occur in the sexually monomorphic White Stork.
Article
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Incubation behaviour is essential for understanding the reproductive success in birds. For example, the orientation of the bird is important for reducing incubation costs associated with wind or sun, but on the other hand can be modified by the perceived risk of predation. We studied the body position of incubating White Stork Ciconia ciconia in eastern Poland using a small unmanned aerial vehicle (drone). The head and body orientation of the incubating storks was non-random and modified by natural factors, mainly wind direction and speed, but also by the presence of an apex predator, the White-tailed Eagle Haliaeetus albicilla . However, head orientation during incubation in nests located on electricity poles was also modified by the presence of the power lines, probably due to disturbance in the magnetic field detected by birds. Surprisingly, although the positioning of incubating birds (mainly females) is very important for the detection of predators and for reducing energy costs, these have not previously been studied. New technologies, such as drones, make it possible to collect new, extensive information on the incubation behaviour of birds.
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We observed unusual feeding behavior of the White Storks Ciconia ciconia: they were seeking food at night. They were eating insects under the street light on the sidewalk in an urban setting. Another unusual behavior observed was catching flying beetles by storks while standing on the nest and platform.
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