Replacement clutches in eagles – some notes and sources
Speaking to the Mitteldeutsche Zeitung
newspaper, a German raptor expert for the Middle Elbe Biosphere Reserve
said recently that a replacement clutch, common in other bird species, doesn´t occur among eagles.
If he has been quoted correctly, the statement is obviously not accurate. The Danish TV-nest example shows that the Scandinavian White-tailed Eagle pair replaced the lost clutch in almost the same time as the Bald Eagles in Northern Florida in the here already mentioned study: “Of 58 pairs that had first clutches removed, 45 (78%) laid a second clutch within an average of 29.4 days” (Wood P.B. & Collopy M.W. 1993).
According to the Hornby Eagle Group Projects Society
, southern Bald Eagle females “attempt second clutches if the first eggs are lost in the early stage of incubation. Females that breed further north have a smaller window of opportunity and appear to attempt second clutches rarely.” Edit: In 2016, "because of unusually severe weather during January and February (...), several pairs of Florida's eagles
have produced second broods." See also: “The Laying of Replacement Clutches by Falconiforms and Strigiforms in North America” by Michael L. Morrison and Brian James Walton, PDF available via Google.
Some sources report successful replacement clutches for European Bonelli´s Eagles
(2009), Booted Eagles (Ignacio S. Garcia Dios, Spain 2001), the Eastern Imperial Eagle (Horal, Czech Republic 2011: “In one case (2006), a fully adult pair laid the eggs as late as the end of April or the beginning of May. This was highly probably a replacement clutch”) and the Black Eagle. In the latter case the observation was possible via webcam ("Black Eagle Beats The Odds As Eaglet Hatches From Second Clutch of Eggs", Africam.com
2013). According to Dixon (1937), replacement clutches of the Golden Eagle “were produced in California some 28 days after the first” (in: The Golden Eagle, Jeff Watson).
Sea Eagle's Nest. Bruno Liljefors 1907, public domain
Ian Newton (Population Ecology of Raptors) states that replacement laying is rare among eagles. In the same book the re-nesting interval for White-tailed Eagles is specified as “19 and 29 days” (his source is Fentzloff, C. Erfolgreiche Zucht und Adoption von Seeadlern (Haliaeetus albicilla). Deutscher Falkenorden 1975:28–40).
According to John A. Love, sea eagles “in captivity have been known to lay a second, replacement clutch if the first is destroyed or removed. The time needed to achieve this is about three weeks, and it usually only takes place if the clutch has been lost at an early stage” (Eagles, John A. Love 1989).
About the Danish eagles
- Wood P.B. & Collopy M.W. (1993) Effects of Egg Removal on Bald Eagle Productivity in Northern Florida. The Journal of Wildlife Management, 57, 1-9
- Garcia Dios, Ignacio S. (2001) Probable replacement clutches by Booted Eagles (Hieraaetus pennatus) in the Tietar River Valley of central Spain. Raptor Res. 35 (4) 75
- David Horal, Eastern Imperial Eagle (Aquila heliaca) in the Czech Republic. Acta zool. bulg., Suppl. 3, 2011: 55-59. (See also: “In two cases, a replacement clutch was laid as late as in the end of April/beginning of May.” David Horal, Imperial Eagle in the Czech Republic. VII. International Conference on the Conservation of the Eastern Imperial Eagle 2- 5 October 2013, Bratislava, Slovakia. Book of Abstracts)
As reported, both eggs of the first clutch in the Danish nest were destroyed by a marten in the early morning of March 20th (05:17) in 2015. The eggs of clutch A were laid egg #1 February 27th (assumption, not confirmed yet), egg #2 March 2nd. Clutch B: Egg #1 April 17th (about 12:30) and #2 April 20th (about 10:15). A video documentation is available, see below. In the early evening of April 23rd there are still two eggs in the nest, so the replacement clutch is probably complete. Edit: Chick #1 hatched in the morning of May 23rd; #2 arrived on May 26th. Both (one male, one female) were ringed on 20 July. Data: Weight: female 5150 g, male 3780 g; length of wing: female 474 mm, male 398 mm; length of tail: female 253 mm, male 175 mm; length of beak, female 64,05 mm, male 58,63 mm (information by Dansk Ornitologisk Forening via Facebook/data translation by forum member b.h-p). The young birds left the nest around August 20th.
The White-tailed Eagle became extinct in Denmark and around the Baltic Sea in the early to mid-20th century. The large raptor disappeared due to persecution in many European regions at that time; in the UK and Ireland even earlier. During the 1950s and 60s the use of DDT and other pesticides in agriculture decimated the remaining WtE population. A first sea eagle pair came back to Denmark in 1995, and since 1996 the White-tailed Eagle is again a breeding species in the country.
In the record year
2014 the Eagle Project within the Danish Ornithological Society (Dansk Ornitologisk Forening/DOF) registered 61 occupied breeding territories. 46 of these pairs raised a total of 83 young (14x1/27x2/5x3). For detailed information (tables, maps, charts) on the current status of the population of the White-tailed Eagle in DK see: DOF publication list 2015, Pedersen, L., E. Ehmsen & I. H. Sørensen (2014), 2015: Projekt Ørn 2014 – årsrapport. PDF available, click here.
2015 is the third Danish eagle-webcam
season. The nest is located on Lolland
, the fourth largest island of Denmark.