White-tailed Eagle Haliaeetus albicilla

DISTRIBUTION AND ABUNDANCE

In Poland the White-tailed Eagle occurs in the following regions: Pojezierze Mazurskie, Pojezierze Pomorskie, Pojezierze Wielkopolskie, Nizina Śląska, Polesie Lubelskie and Kotlina Sandomierska. The species also has single breeding sites in the Karkonosze Mts and Wyżyna Śląska.

The most numerous White-tailed Eagle population occurs in Pomorze Zachodnie (142-180 pairs), the largest concentration of pairs being recorded around Zalew Szczeciński, in Pojezierze Myśliborskie and Pojezierze Drawskie. The density of this population is the highest in Poland (e.g. 7-9 pairs nested in an area of 13 km2, the minimum distance between two simultaneously occupied nests amounting to a mere 250 m).

Table 1. Numbers and distribution of the White-tailed Eagle Haliaeetus albicilla breeding population in Poland at the end of the 90s.

Region	Number of known pairs	Estimated number of pairs
Pomorze Zachodnie	126-142	142-180
Polska NE	111-125	125-140
Śląsk	42-49	49-50
Wielkopolska	43-45	45-50
Pomorze Środkowe	27-31	31-35
Lubelszczyzna	19-22	22-25
Polska Centralna	4-6	6-10
Nizina Północnopodlaska	10	10
Total	382-430	430-500

The second region abundant in White-tailed Eagles is NE Poland, with 135-150 pairs and a density of 0.33-0.37 pairs/100 km2. In the mesoregions of Pojezierze Olsztyńskie, Pojezierze Mrągowskie, Pojezierze Iławskie, Równina Mazurska and Kraina Wielkich Jezior Mazurskich (Masurian Lakeland) (a joint surface of 13 696 km2, 38% of the study area) occurrence of 92-102 pairs (75% of the populations inhabiting this part of the country) has been established, the mean density reaching 0.67-0.74 pairs/100 km2 (locally even 1.73 p/100 km2; in the Masurian Landscape Park as many as 2.8-3.3 pairs/100 km2 bred in an area of 722 km2).

The White-tailed Eagle is relatively abundant in Wielkopolska (45-50 breeding territories), the main regions of its occurrence including Pojezierze Lubuskie, Pojezierze Poznańskie and Puszcza Rzepińska. Comparable numbers have been found in Śląsk (49-50 pairs). The main breeding grounds here are situated within Bory Dolnośląskie, the Barycz River valley and Równina Oleśnicka.

In Pomorze Środkowe the White-tailed Eagle numbers were estimated at 31-35 pairs. The species occurs mostly in Pojezierze Drawskie and Pojezierze Kaszubskie as well as in the Słowiński National Park. It is slightly less numerous in the region of Lublin (22-25 pairs). In Central Poland the abundance is estimated at 6-10 pairs.

The data available allow to make only a rough estimation of fluctuations in the White-tailed Eagle numbers within the two last centuries. The species is known to have got extinct in the majority of the Polish territory by the end of the 19th century. Only a dozen or so pairs survived in Pomorze Zachodnie and single ones in Pomorze Środkowe, Zalew Wiślany and Puszcza Piska. Presumably, ca 30-40 pairs nested in our country then. At the beginning of the 20th century a total number of 20 pairs at most occurred in Poland. In the 1960s the species abundance was estimated at ca 50-100 pairs. In the subsequent decade the population probably declined mainly due to the birds getting poinsoned by the DDT, which was commonly used in agriculture, and by preparations containing heavy metals. However, as early as the mid 80s the numbers of the White-tailed Eagle started to grow again and new breeding sites were discovered in Pojezierze Myśliborskie, Pojezierze Lubuskie, Pojezierze Mazurskie, Nizina Śląska, Bory Dolnośląskie, Podlasie and Pomorze. The species population was then estimated at 120-140 pairs. In the second half of the 80s at least 185 pairs were observed, the estimates reaching 210-240 pairs.

According to the latest data, from the end of the 90s, there are 380 confirmed and 50 probable breeding territories of the White-tailed Eagle in Poland, with 380-430 breeding pairs (table 1), which yields a mean density of 0.12-0.14 pairs/100 km2. Taking into account birds of unknown breeding status, the abundance can be assessed at 430-500 pairs.

A clear growth of the White-tailed Eagle population in our country is mainly consequent on the implementation of legal protection, of nests and nest-sites in particular, as well as cessation of the DDT usage and reduction of plant protection chemicals application in agriculture and forestry. The relatively high nesting success is also conducive to the population development.

MONITORING

The results of monitoring conducted in 2001 and 2002 are given in table 2. In 2001, the controls covered 449 nests, in 20 (4.5%) of which the zone protection regulations were found broken. In 2002, the zone protection law was violated at 35 (6.2%) of the 562 nests controlled.

Table 2. Results of controls to the White-tailed Eagle breeding sites in Poland in 1999 and 2000. (1) - total number of controlled sites, (2) - total number of controlled nests, (3) - number of sites where birds were recorded, (4) - number of nests at which zone protection regulations were found violated, (5) - number of nests newly found in the territories known from previous years, (6) - number of newly found territories with a nest, (7) - number of newly found territories without a nest

Region	Controlled sites (1) 2001 2002	Controlled nests (2) 2001 2002	Sites with birds (3) 2001 2002	Regulations violated (4) 2001 2002	New nests in territory (5) 2001 2002	New territory with nest (6) 2001 2002	New territory without nest (7) 2001 2002
Pomorze Środk.	16 31	23 35	12 22	- -	- -	- 2	- 1
Pomorze Zach.	124 166	191 218	101 122	2 8	7 17	3 5	- -
Wielkopolska	92 103	114 126	85 94	1 8	7 20	11 7	4 4
Śląsk	19 56	19 57	17 47	5 -	- 5	1 8	- -
Lubelszczyzna	25 26	38 39	23 25	- -	8 7	1 1	- 1
Polska Centralna	17 18	15 19	12 11	1 1	- -	1 2	- -
Polska NE	52 115	88 146	44 101	9 14	8 12	1 4	1 2
Nizina Północnopodlaska	10 10	12 12	10 10	2 3	1 -	2 -	- -
Razem	355 525	500 652	304 432	20 35	31 61	20 29	5 8

REPRODUCTIVE PARARMETERS

The current conditon of the White-tailed Eagle Polish population is good, and its further growth and territorial expansion can be expected. The good condition of the population is also evidenced by the number of fledglings per pair with known brood result, equalling 0.83 on average. This parameter at the level of 0.7 young per pair is believed to ensure population stability.

The White-tailed Eagle breeding results in 1999, 2000 and 2001 are as follows:

	1999	2000	2001
Number of occupied nests with known breeding results	303	333	232
Number of successful nests	188	198	157
Nest success (%)	62,0	59	67
Total number of fledglings	278	287	230
Mean number of fledglings per occupied nest	0,92	0,86	0,99
Mean number of fledglings per successful nest	1,48	1,45	1,46
Number of nests with: 3 nestlings	2 (1,1%)	3 (1,5%)	6 (3,8%)
2 nestlings	86 (45,7%)	84 (42,2%)	61 (38,9%)
1 nestling	100 (53,3%)	112 (56,3%).	90 (57,3%)