PwG OTOP - Południowowielkopolska Grupa OTOP

Tryjanowski P., Sparks T.H. & Jerzak L. (eds.)
The White Stork in Poland: studies in biology, ecology and conservation
Bogucki Wydawnictwo Naukowe, Poznań 2006
“Close to Storks” – a project of on-line
monitoring of the White Stork Ciconia ciconia nest
and potential use of on-line monitoring
in education and research
Paweł T. Dolata
South Wielkopolska Group of the Polish Society for the Protection of Birds, Wrocławska 60A/7,
PL-63-400 Ostrów Wielkopolski, Poland, e-mail: makri25@poczta.onet.pl
ABSTRACT: This paper describes the on-line monitoring project “Close to Storks”, carried out
by the South Wielkopolska Group of the Polish Society for the Protection of Birds. The monitored nest of the White Stork Ciconia ciconia is situated in the village of Przygodzice, near the
town of Ostrów Wielkopolski (South-Western Poland). The main aim of the project was
popularisation of ecological issues. Over the five months of the 2006 breeding season more
than 660,000 people from 84 countries visited the website www.bociany.ec.pl with the image of the nest. Polish media were also keenly interested in the project. From the research
perspective, camera monitoring provides a good opportunity to collect breeding biology and
ecology data, which is difficult (or even impossible) to obtain by standard methods. Preliminary results collected in 2006 are presented, including the first precise observation of egg
laying by White Stork in Poland and a clear case of parental infanticide. Intervals between
successive eggs laid by the female were about 45–48 hours. The female laid eggs at night.
Potential applications and problems entailed by camera monitoring are discussed. Using
this method should involve full video-recording of subjects and collaboration with ornithologists.
KEY WORDS: Ciconia ciconia, ecological education, on-line monitoring, breeding biology,
breeding ecology, parental infanticide, egg laying
Introduction
The White Stork Ciconia ciconia is one of the most popular bird species in Poland
(Sokołowski 1958, Lewandowski & Radkiewicz 1991, Dolata 2006) and for this
reason it seems to be an appropriate species for the purpose of increasing interest
in birds and nature protection problems in Poland.
438
Paweł T. Dolata
Although the White Stork is also one of the most extensively studied bird in Poland, some details of its biology and ecology are unknown or unclear (e.g. Ptaszyk
1998, Antczak & Dolata 2006, Kania 2006, Profus 2006). Between the years
1971–2000, according to the Wildlife & Ecology Studies Worldwide, 737 ornithological papers about the White Stork were published in Poland (Kopij 2005), but a
large majority of them concerned only population size, distribution and breeding
success. There are only a few Polish papers that focus on other aspects of the White
Stork’s breeding biology (e.g. Mrugasiewicz 1972, Profus 1986, 1991, 2006,
Radkiewicz 1992).
Some data, such as that concerning egg laying can be collected accurately by
monitoring nests with a camera, like it was done in Germany (Hoffmüller 2001).
This paper reports the first results obtained in the “Close to Storks” on-line project, led by the South Wielkopolska Group of the Polish Society for the Protection
of Birds (Południowielkopolska Grupa Ogólnopolskiego Towarzystwa Ochrony Ptaków,
PwG OTOP), which aimed to be an example of its scientific usefulness.
Methods
th
On the 24 of March, 2006, before storks returned to their breeding grounds, a
small digital TV-camera was installed on a chimney 1.5 m above White Stork nest.
The nest is located in the village of Przygodzice (51°35' N, 17°49' E) near Ostrów
Wielkopolski (the Wielkopolska region), on the edge of the Barycz River Valley.
The area is part of the Barycz Valley Landscape Park and of a Special Protected Area
of the Natura 2000 network of the European Union. The Barycz River Valley was
the feeding area for the observed pair. Additionally, while nestlings were ringed on
the 19th of June, a microphone was installed by the nest (Phot. 1). The camera was
fixed on an arm, which did not hamper the birds with landing or taking off from the
nest (Fig. 1). Throughout the entire breeding season the birds’ behaviour did not
appear to be affected by the equipment (see Phots. 1 & 2).
The camera image (Phot. 2), refreshed every 2–5 seconds, and the sound from
the available on-line initially on the PwG OTOP website www.pwg.otop.org.pl and
later on the specially created website www.bociany.ec.pl, and also as a continuous
image (streaming) via ITTV Interactive Television. As the camera had the infra-red
function, the storks could be tracked also at night.
Details of the storks’ activity in the nest were recorded from the camera on-line
image by:
– four project members (Marcin Rachel, Eva Stets-Vithoulka, Sv tlana Vránová
and author);
– volunteer internauts who responded to an invitation to cooperation placed on
the website, which outlined the aim and importance of observations and reports of the page viewers. The website enjoyed great popularity, being visited a
few thousands times a day (up to 12,500). Therefore, it seemed advantageous
to take the opportunity and invite visitors to collaboration. Support of these
voluntary observers was important because long time observation of the nest
was difficult to carry out by one or two observers.
“Close to Storks” – a project of on-line monitoring of the White Stork nest
439
Phot. 1. The monitored nest with one-month nestlings, the microphone and the camera,
th
19 June 2006. The Barycz River Valley in the background. Photo: Paweł T. Dolata
440
Paweł T. Dolata
th
Phot. 2. Screenshot of the monitored nest with displaying adults and eggs, 19 April 2006.
Photo: Marcin Rachel
Educational aspect
During the five months of the 2006 breeding season (April–August) more than
660,000 people from 84 countries visited the website www.bociany.ec.pl, where
the camera image of the nest was transferred, which made up nearly 1,300,000 visits. Various Polish media were also greatly interested in the project. More than 100
articles, notes or news broadcasts concerning the project were published in popular TV and radio channels, on websites, and in national as well as regional newspapers. The 1st Meeting “Close to Storks” in Przygodzice, which took place between
22–23 July 2006, was part of the project and was attended by approximately 70 participants. Feedback from internauts such as e-mails to the organizers of the project, opinions in the guest book on the website and a discussion forum indicated
that the project “opened the eyes of ordinary people” for the birds and nature (majority of which were not birdwatchers or nature-lovers).
Initial research results
The initial results are given in Table 1. First, short visits of the monitored nest were
done by not the same birds which occupied this nest for breeding season – on 28th
“Close to Storks” – a project of on-line monitoring of the White Stork nest
441
Table 1. Selected data concerning the on-line monitored White Stork nest in Przygodzice,
in 2006
Date
Hours
Short visits of the first White
Storks at the nest
Observed event
28.03
05.04
14.10
12.20
Nest occupied by a pair
08.04
13.13
First copulation
st
1 egg laid
08.04
14.06
14.04
00.30–01.26
2nd egg laid
15.04
21.51–22.18
3rd egg laid
17.04
21.31–23.01
4th egg laid
19.04
20.01–20.14
5th egg laid
21.04
21.15
First documented event
of alternate incubation
24.04
st
1 nestling hatched
nd
18.05
The first change-over photographed, later change-over
observed frequently afterwards
02.10–04.49
2 nestling hatched
18.05
09.30–11.30
3rd nestling hatched
19.05
before 04.47
4th nestling hatched
21.05
before 04.54
5 nestling hatched
22.05
16.42–17.13
One nestling disappeared
from the nest
29.05
A living chick struck by
a parent with its bill and
thrown out of the nest
30.05
First fledged young
22.07
th
Last night with all three
young in the nest
09/10.08
First night without any
stork in the nest
16/17.08
Last nights with one stork
in the nest
17/18.08
18/19.08
Nest without birds
since 19.08
Notes
each visit lasted only a few
minutes
During a storm, probably
pushed out by the wind
(transmission error – no view
from the camera)
13.08
The smallest nestling of the
four, moving only slightly
from the morning onwards,
but alive in the moment of attack (observer via www: M.
Bociański); found dead on the
ground (T. Wojtasik)
15.07, 15.07 Probably frightened by a
and 15.09 “stork-lover” who came too
close to the nest and waved
his hands to the camera
Last stay of all the three in
the nest
Age of the bird not known
442
Paweł T. Dolata
March it was with no doubt the bird which the same day started occupy another
nest in Przygodzice. For egg laying and nestling hatching two times are given: the
last observation before a new egg or nestling appeared and their first observation
(e.g. on the 14th of April the last observation of the nest without eggs was at 00.30
and the first observation of an egg was at 01.30, when the female stood up). The female laid the first egg on the 7th day after arrival to the nest and the first copulation.
The next 4 eggs were recorded at about 45, 48-, 45- and 48-hour intervals, respectively. The female was laying the eggs at night or in the evening (as was the case
with the fifth egg). Since April 24th it was frequently recorded that the parents incubated the eggs alternately.
With the presumption that three first hatched nestlings survived to fledging,
based on general breeding ecology of the species (Profus 2006) and small body size
of disappeared and killed chick, they first successful flights was done on 66th, 66th
th
and 67 day of life, respectively. Even flying during the days, they roosted on the
nest regularly 19–25 consecutive nights (Table 1).
A wider report of behavioural data collected in the project will be prepared by
Sv tlana Vránová.
Discussion
Observed cases of early spring, short visits of birds which not stayed here for
breeding season agree with data of Wuczyński (2005), that such cases are common. First arrivals of storks on the nest are such important event for the village
people (as “sign of spring”) that it stayed in their memory, questionnaires or notes
and are reported to the scientist as occupations of the nests – it may be source of
important error in such data (see also Mrugasiewicz 1972). Clear instructions
must be included in the inquiries or detailed interview must be done by researches
to avoid such errors.
The observed pair occupied the nest in the peak of the arrival time typical of the
White Storks in Poland (Profus 1991, 2006, Radkiewicz 1992, Ptaszyk 1994). Time
from the arrival of the second bird (occupation of the nest by the pair) to the first
egg laying was also typical. In the breeding colony in Kłopot and in adjacent areas
(W Poland) the first egg was laid 1–9 days (in one case 11 days) after the arrival of
the second partner on the nest, and in 60.6% of the cases 3–4 days (Radkiewicz
1992) and in Upper Silesia (S Poland) the commencement of breeding occur in the
average 10±0.82 days (SE) after the arrival of the second partner on the nest
(N = 9, Profus 2006). Time of egg laying in the monitored pair was relatively early.
In other studies (all of them were carried out in South-Western Poland, as in the
case of the monitored nest, but most of them had a more southern location) females began laying eggs later: in the district of Milicz, between 1959–1968 less
than 10% females started laying before April 15th; between 1973–1978 in Upper
Silesia the average laying date was the 30th of April (Profus 1991) and in the province of Legnica in 1987 the first egg was laid between the 15th of April and the 4th of
May (K. Kujawa, after Profus 1991). Data from studied nest are similar to the new
data from Upper Silesia: during the period 1992–2002 the most intensive egg lay-
“Close to Storks” – a project of on-line monitoring of the White Stork nest
443
ing (about 60% of pairs) occurred between 11th and 25th April and during the period 1990–2002 the average date of laying the first egg was 20th April (Profus
2006). Such earlier laying date of the monitored pair could be linked to a generally
earlier laying date observed in the White Stork in the recent years (Ptaszyk et al.
2003, Profus 2006).
Before the project was started, the most accurate data about the laying date of
the White Stork in Poland was established by means of direct nest controls carried
out every second day (Radkiewicz 1992). Less accurate data (up to one week or 4–6
days) was obtained by means of water tests (Majewski 1980) performed during a
control of a nest (Profus 1991, 2006). Laying date was also estimated from the
time of fledging, basing on a much smaller sample of multiple (we do not know
how frequent) direct controls of 39 nests (Mrugasiewicz 1972). Such methods are
sufficient to provide a general view of the breeding ecology of the species but they
do not allow to obtain as precise data as it is possible with a camera.
Sokołowski (1958) and Makatsch (1974) report that female White Storks laid
eggs at 48-hour intervals. A more detailed study conducted by Radkiewicz (1992)
revealed some variation in the laying interval: most of the eggs were laid at two-day
intervals but some of them at one- or three- day intervals (19.4% and 0.9%, respectively). We should bear in mind that the study method classified an egg laid 15
minutes after control as an egg laid after a one-day interval. Also, a review of the
Western Palaearctic literature published by Cramp (1998) reports that “eggs are laid
at intervals ranging from 1 to 4 days, most typically 2”.
One of the problems during the observation was that the precise laying time
was impossible to pinpoint as most of the time the eggs were obstructed by the incubating female, especially in the second stage of the laying period. The number of
eggs could be established only when the adult stood up. Therefore, in Table 1 two
times are given for each egg: the last moment without the egg while nest bottom
could be seen and the first time when the egg was observed.
We noted an incidence of a chick being thrown out by a parent. Before this took
place, several observers reported on the chick’s condition; however, only two of
them noticed the actual moment of rejection of alive bird (M. Bociański and one
anonymous observer from St Petersburg). This clearly shows that a flaw in this
project was that the camera image was not recorded continuously. Even participation of more observers cannot substitute for systematic, continuous recording of
the camera image and it should be crucial in on-line monitoring projects.
Parental infanticide, which took place probably in the 9th or 10th day of the
chick’s life (assuming that the chick, which was the smallest of the four, hatched as
the fourth or fifth) occurred at a typical age. In Spain the average nestling age when
parental infanticide was observed was 7.3 days (Tortosa & Redondo 1992).
For over a hundred years Polish researchers studying the White Stork have discussed whether adult birds kill (throw out from the nest) their offspring or not
(e.g. Wodzicki 1877, Sokołowski 1932, Czudek 1935, Ołtuszewski 1937). As early
Sokołowski (1932) noticed that a chick found under the nest could have fallen out
due to struggle for food between the nestlings. As he puts it, “the folk people, who
have fertile imagination, claim that adult storks throw out their chicks themselves, when they
444
Paweł T. Dolata
decide that the young will not bring any profit”. Nowadays it is known that parental infanticide does occur in the White Stork and we partly understand what causes this
behaviour (Sokołowski 1958, Tortosa & Redondo 1992, Sasvári et al. 1999a, Zieliński 2002). However, no case of parental infanticide has been recorded throughout the author’s 13-year studies on the White Stork in the Ostrów Wielkopolski
district, which included systematic and detailed interviews of “nest owners” (people living close to the nest). There have indeed been, though, a few clear cases of a
chick falling out of nest accidentally, as a result of struggles between the young. Regarding every nestling found under a nest as thrown out by its parents may cause a
large methodological error in a study of brood loss. Even a larger error, resulting in
overestimation of parental infanticide is treating parents as killers of their young
and cause of brood loss. Papers by Jakubiec (1991) and Guziak & Jakubiec (2006)
do not provide information on what basis parents were treated as the agents of
brood loss in the nest. At least 1121 broods were regarded as affected by parental
infanticide (Guziak & Jakubiec 2006). On the basis of data collected in yearly
White Stork nest censuses conducted between 1970–1985, which also included interviews of owners of houses with storks’ nests, Jakubiec (1991) estimated that
brood reduction by parents took place in 110 (34.1%) out of 323 cases of chicks’
death and did not report any case of young falling out from their nest. However, almost all of the material was obtained only by means of interviews of villagers – the
“nest owners” (registered by researchers who counted nests or by village mayors).
Data obtained by Guziak and Jakubiec (2006) was collected using the same
method. Field research was carried out and questionnaires were sent out to village
mayors (and not directly to nest owners, who provide more reliable information –
see Kujawa 1991) and schools, but a primary source of data on brood loss were in
almost all cases people living in the nest’s neighbourhood.
It is very difficult to observe the exact moment when a chick is thrown out or
falls out of nest without continuous nest observation, and it is clear that “nest
owners” do not make such observations. Even when an accidental observer is lucky
enough to spot this moment, they practically are not able to tell whether the chick
was killed by a parent or died in the nest and then was thrown out. Out of 17 papers on White Storks living in various Polish provinces, which were published by
Guziak and Jakubiec (2006), only one (Ptaszyk 2006) noticed such probability.
Lacking personal observation, the interviewed villagers may have provided a biased, anthropomorphic view of nestlings being thrown out from their nest by their
parents, when the latter “know” that it is going to be “a hard year” and that “they
won’t be able to feed all their offspring” (Wodzicki 1877, Sokołowski 1931, Ołtuszewski 1937, Lewandowski & Radkiewicz 1991, own data). Information coming from
folk people, in most cases not verified by a direct interview is then used as material
in scientific papers.
Jakubiec (1991) claims that the data in his paper can be regarded as reliable, but
it was difficult to determine precisely the true cause of offspring loss. It was shown
that data from surveys investigating as simple issues as the number of nests occupied by White Stork pairs or the number of young that fledged the previous year,
are not accurate and have limited value (Zieliński & Andrzejczak 1991). They are
“Close to Storks” – a project of on-line monitoring of the White Stork nest
445
of even less value in breeding biology, especially in the case of difficult to observe,
short events such as parental infanticide. Kujawa (1991) said: “Even in the case of a
species that is as well known as the White Stork, the only true information from the surveys is
the presence of a White Stork nest in the locality in question”.
Moreover, parental infanticide was not recorded during more detailed studies,
such as the three-year study conducted in Hungary by Sasvári et al. (1999b), although it was recorded in seven cases out of 37 in continuously monitored White
Stork nests in Spain (Tortosa & Redondo 1992).
As a matter of fact, in spite of the large number of papers about White Stork
breeding success in Poland (see above), probably only one clear and detailed case
of parental infanticide, studied as in the Black Stork Ciconia nigra (Kłosowski et al.
2002), was reported by a qualified observer (Borowski 1963). Part of the papers in
Jakubiec (1985) reported only the number of eggs and nestling thrown out of
nests, without discussing possible causes of these incidents due to lack of sufficient data. However, in the book by Guziak and Jakubiec (2006), which was based
on material collected in a similar fashion, more than thousand cases of offspring
loss are reported as parental infanticides. It is important to note that in a detailed
study performed in Upper Silesia by Profus and Chromik (2001), which was based
on field observation and surveys and focused on breeding aspects (including
causes of nestlings’ death), the authors did not find any case of parental infanticide
in a total of 304 dead nestlings; in 127 of them the cause of death was “unknown
(dead nestling was found in or under a nest)”. Using additional cases of nestlings’ death
from this area, Profus (2006) still did not find any case of parental infanticide in a
total of 392 dead nestlings. No case of parental infanticide was confirmed. A cautious approach should be adopted when we have no clear evidence of parental infanticide. Data from camera monitoring can help to establish how frequently the
true parental infanticide occurs in the White Stork in Poland.
A very important characteristic of the camera monitoring method is its non-invasiveness as opposed to direct controls of the nest, especially over such key periods as laying or incubating eggs.
One of the main problems with research application of cameras in the White
Stork nests in Poland is lack of good cooperation between scientists and camera
monitoring projects. The main goal of these projects is popularisation of knowledge about the monitored subjects, and sometimes promotion of the project’s organising body; still, achieving this aim may as well include cooperation with and
support of researchers. The first on-line White Stork nest camera project in Poland, led by an informal group of “stork lovers”, was launched in 2004 in the Chyby
village near Poznań (www.bociany.kalinski.pl). The project’s authors, however, did
not take this opportunity to carry out a scientific research. Cooperation with researchers seems to be important or even necessary in all on-line monitoring projects, not only in the case of the White Stork (for instance, in Poland the first projects with the Kestrel Falco tinnunculus nest cameras have just been started).
Camera monitoring of a nest appears to be useful in resolving some problems in
breeding and feeding biology, as well as in behavioural ecology of the species, including:
446
–
–
–
–
–
–
–
–
–
Paweł T. Dolata
accurate time of egg laying and hatching;
participation of the male and the female in incubation, including night incubation – Sokołowski (1958) suggested that only the female incubates at night;
amount, type and frequency of food delivered to the nest by each of the parents,
which is very important due to lack of such data in Poland (Kosicki et al. 2006);
changes of parental care during different age of nestlings;
food competition between nestlings;
social relations between adult and young storks;
interaction with alien storks (including nest defence);
detailed picture of parental infanticide and discriminating between cases of falling out of nest and being thrown out of nest;
precise length of the offspring’s stay in the nest from fledging to leaving the
nest.
Acknowledgements
I want to thank the Przygodzice Community Office and its Chief Mr. Przemysław
Kaźmierczak for financial and technical support of the project; to Telekomunikacja
Kolejowa Sp. z o.o., Przedsiębiorstwo “Pro-Art”, REXE and Telewizja Interaktywna
ITTV firms for technical support; Marcin Rachel, Marek Radziszewski, Tomasz
Świątek and Tomasz Wojtasik for their cooperation in the project; and Maciej
Bociański, Marcin Rachel, Sv tlana Vránová, Eva Stets-Vithoulka and others for
data collection.
References
Antczak M., Dolata P.T. 2006. Night roosts, flocking behavior and habitat use of the
non-breeding fraction and migrating White Storks Ciconia ciconia in the Wielkopolska region (South-Western Poland). In: Tryjanowski P., Sparks T.H., Jerzak L. (eds.) The White
Stork in Poland: studies in biology, ecology and conservation. Bogucki Wyd. Nauk.,
Poznań: 209–224.
Borowski S. 1963. Effect of oecological agents on the breeding of the White Storks Ciconia
ciconia in Białowieża in 1960. Prz. Zool. 7: 60–62.
Cramp S. (ed.) 1998. The Complete Birds of the Western Palearctic on CD-ROM. Oxford
Univ. Press, Oxford.
Czudek A. 1935. [The White Stork (Ciconia ciconia cic. L.) in Silesian voivodeship]. Wyd.
Muz. Śląskiego w Katowicach. Dział III, 8: 5–44.
Dolata P.T. 2006. The White Stork Ciconia ciconia protection in Poland by the tradition, customs, law and active efforts. In: Tryjanowski P., Sparks T.H., Jerzak L. (eds.) The White
Stork in Poland: studies in biology, ecology and conservation. Bogucki Wyd. Nauk.,
Poznań: 477–492.
Guziak R., Jakubiec Z. (eds.) 2006. White Stork Ciconia ciconia (L.) in Poland in 2004. Results of the VIth International White Stork Census. PTPP “pro Natura”, Wrocław.
Hoffmüller U. 2001. Zur Brutbiologie des Weißstorchs – Ergebnisse einer Diplomarbeit. In:
Kaatz Ch., Kaatz M. (eds.) 2. Jubiläumsband Weißstorch. Tagungsbandreihe des
Storchenhofes Loburg. Staatliche Vogelschutzwarte im Landesamt für Umweltschutz
Sachsen-Anhalt: 284–289.
“Close to Storks” – a project of on-line monitoring of the White Stork nest
447
Jakubiec Z. 1991. Causes of breeding losses and adult mortality in White Stork Ciconia
ciconia (L.) in Poland. Studia Nat. A 37: 107–124.
Kania W. 2006. Movements of Polish White Storks Ciconia ciconia – an analysis of ringing results. In: Tryjanowski P., Sparks T.H., Jerzak L. (eds.) The White Stork in Poland: studies
in biology, ecology and conservation. Bogucki Wyd. Nauk., Poznań: 249–294.
Kłosowski G., Kłosowski T., Zieliński P. 2002. A case of parental infanticide in the black
stork Ciconia nigra. Avian Science 2: 56–59.
Kopij G. 2004. Status of ornithological studies in Poland and in the world on the threshold
of the 21st century: a bibliometric analysis. Not. Orn. 45: 109–114.
Kosicki J. Z., Profus P., Dolata P. T., Tobółka M. 2006. Food composition and energy demand
of the White Stork Ciconia ciconia breeding population. Literature survey and preliminary
results from Poland. In: Tryjanowski P., Sparks T.H., Jerzak L. (eds.) The White Stork in
Poland: studies in biology, ecology and conservation. Bogucki Wyd. Nauk., Poznań:
169–183.
Kujawa K. 1991. Usefulness of the inquiry method in population studies of the White Stork.
Not. Orn. 32: 105–114.
Lewandowski A., Radkiewicz J. 1991. Bocian w mowie i kulturze. Wyd. WSP, Zielona Góra.
Majewski P. 1980. Method for estimating the age of mallard’s (Anas platyrchynchos L.) embryos by floating the eggs in water. Wiad. Ekol. 26: 151–158.
Makatsch W. 1974. Die Eier der Vögel Europas. Bd I. Neumann Verlag, Radebeul.
Mrugasiewicz A. 1972. White Stork, Ciconia ciconia (L.) over the district of Milicz in the years
1959–1968. Acta Orn. 13: 243–278.
Ołtuszewski W. 1937. The White Stork in Kościan and Leszno districts. Wyd. Okr. Kom.
Ochr. Przyr. Wielkop. Pom. 7: 143–160.
Profus P. 1986. Zur Brutbiologie und Bioenergetik des Weißstorch in Polen. Beih. Veröff.
Naturschutz. Landschaftspflege Bad.-Wütt. 43: 205–220.
Profus P. 1991. The breeding biology of the White Stork Ciconia ciconia (L.) in the selected
area of Southern Poland. Studia Nat. A 37: 11–57.
Profus P. 2006. Population changes and breeding ecology of the White Stork Ciconia ciconia L.
in Poland against a background of the European population. Synthesis. Studia Nat. 50:
1-155.
Profus P., Chromik W. 2001. The breeding population of the White Stork Ciconia ciconia (L.)
in Upper Silesia and surrounding areas. I. Present state, numerical changes and breeding
effects in the former districts of Pszczyna and Tychy. Chrońmy Przyr. Ojcz. 57, 6: 28–57.
Ptaszyk J. 1994. Spring arrival of the White Stork Ciconia ciconia in Wielkopolska region in
1983–1992. Pr. Zakł. Biol. Ekol. Ptaków UAM 3: 149–164.
Ptaszyk J. 1998. What directions should investigations of the Polish White Stork Ciconia
ciconia population follow? Prz. Przyr. 9, 3: 65–76.
Ptaszyk J. 2006. The White Stork in Wielkopolska province in 2004. In: Guziak R., Jakubiec
Z. (eds.) White Stork Ciconia ciconia (L.) in Poland in 2004. Results of the VIth International White Stork Census. PTPP “pro Natura”, Wrocław: 330–360.
Ptaszyk J., Kosicki J., Sparks T.H., Tryjanowski P. 2003. Changes in the timing and pattern of
arrival of the White Stork Ciconia ciconia in western Poland. J. Orn. 144: 323–329.
Radkiewicz J. 1992. Die Phänologie und Ausgewählte Fragen der Nidobiologie des
Weiszstorches Ciconia ciconia (L.) in Kłopot und der Umgebung (Wojewodschaft Zielona
Góra). Przyr. Środk. Nadodrza 2: 79–98.
Sasvari L., Hegyi Z., Hahn I. 1999a. Reproductive performance of White Storks Ciconia
ciconia breeding at low and high densities. Folia Zool. 48: 113–121.
Sasvari L., Hegyi Z., Peczely P. 1999b. Brood reduction in White Storks mediated through
asymmetries in plasma testosterone concentrations in chicks. Ethology 105: 569–582.
Sokołowski J. 1932. Czy bocian w Polsce wymiera? Ochr. Przyr. 12: 1–8.
448
Paweł T. Dolata
Sokołowski J. 1958. Ptaki Ziem Polskich. Vol. II. PWN, Warszawa.
Tortosa F.S., Redondo T. 1992. Motives for parental infanticide in White Stork Ciconia ciconia.
Ornis Scand. 23: 185–189.
Wodzicki K. 1877. [Ornithological notes. I. The Stork. Second edition.]. Drukarnia “Czasu”,
Kraków.
Wuczyński A. 2005. The turnover of White Storks Ciconia ciconia on nests during spring migration. Act. Orn. 40: 83–85.
Zieliński P. 2002. Brood reduction and parental infanticide – are the White Stork Ciconia
ciconia and the Black Stork Ciconia nigra exceptional? Acta Orn. 37: 113–119.
Zieliński P., Andrzejczak S. 1991. An attempt to estimate the credibility of the White Stork
nests counts acquired with the survey method. Not. Orn. 32: 143–148.