Lambs not a significant food source for reproducing White-tailed Eagles in Scotland
New research study discovers percentage of nests with proof of lamb as victim decreases over 20-year duration
A brand-new research study evaluating the diet plan of reproducing White-tailed Eagles ( Haliaeetus albicilla)– likewise referred to as Sea Eagles– in Scotland in between 1998 and 2017 has actually discovered that marine victim of seabirds and fish is the most essential food source for them, whilst the event of lamb in their food has actually reduced as more sets have actually developed.
Analysis of food stays reveals an exceptionally varied diet plan throughout the reproducing season; 11,375 various food products were taped in 293 samples from nest websites in 92 White-tailed Eagle areas throughout Scotland and 121 types were taped with 70 types of bird, 17 types of mammals and a minimum of 30 types of fish.
The research study, released as a peer evaluated paper “ The reproducing season diet plan of White-tailed Eagles in Scotland” in the Scottish Ornithologists’ Club journal Scottish Birds, started in 1998 when there were just 18 sets of White-tailed Eagles in Scotland, primarily in the Inner Hebrides. By 2017 there were at least 122 sets throughout the nation, and 58 nests were tested because year.
The analysis revealed that because time the percentage of lamb stays in nests have actually reduced; at the start of the research study duration in between 1998 and 2002, 15 nests were tested and lambs represented more than 30% of products in 5 of those nests[ie in 33% of nests] As the White-tailed Eagle population broadened, sets developing in brand-new areas tended to feed on less lambs, so by the end of the research study in 2017 lambs accounted for 30% or more of products at 5 of 58 nests tested .
Note– brackets in vibrant included by Mark Avery for information
White-tailed Eagles are significant scavengers, with unskilled birds from the preliminary of releases in the 1970s and 1980s drew in to locations where dead sheep or lambs were easily offered. When currently dead and as carrion, a previous research study discovered that lambs tended to be scavenged. That research study likewise suggested that on event live lambs were eliminated, nevertheless that these lambs taken were frequently smaller sized than typical so more susceptible to predation.
Despite numerous hours of field observations in other tracking of White-tailed Eagles the scale of live lamb predation has actually shown extremely hard to measure. Following the initial settlement pattern on the islands of Mull and Skye in specific subsequent generations started reproducing in locations where natural live victim was quicker offered, with a shift in diet plan as an outcome. In its conclusion the paper mentions that “the formerly prevalent view that lambs are an essential food for White-tailed Eagles has actually been superseded; the dominating proof now is that marine products (fishes and seabirds) are the most essential breeding season food in Scotland.”
The most typical types discovered in nests is now Fulmar– 30% of products per nest– with lamb now just representing 6% typically. As this research study was based upon victim stays, fish, young birds and smaller sized products are most likely to be under-represented in it as these remains are more quickly absorbed or disintegrated. The outcome is that this research study will have over-estimated the significance of big mammals and birds in the diet plan.
The research study likewise taped distinctions in diet plan based upon the geographical place of the nests, supporting previous research studies that reveal White-tailed Eagles are generalist foragers– taking a vast array of victim types– and able to adjust their diet plan to what is easily offered in your area. At seaside areas seabirds and fish comprised the majority of the food stays. At nests in areas even more in inland foods such as wetland birds and bunnies controlled. The research study authors keep in mind that as White-tailed Eagles continue to recolonise historical areas far from the coast types such as Mountain Hare and freshwater fish are most likely to end up being essential food sources.
The paper is an essential contribution to the growing body of understanding about the diet plan of these birds with robust field information and analysis essential in feeding into policy and management, such as the Sea Eagle Management Scheme (SEMS) promoted by NatureScot to support farmers and crofters in locations where White-tailed Eagles exist. The SEMS is because of be evaluated and upgraded in 2024.
The paper authors highlight that as the research study technique concentrated on nests where breeding achieved success, future research studies utilizing tracking gadgets on eagles to keep track of foraging behaviour and recognize feeding perches will be required to assist recognize food remains of immature or juvenile birds, and adult birds outside the reproducing season. Robin Reid, among the paper authors stated: “ This publication has actually been enabled through partnership in between numerous scientists and fieldworkers and with assistance from a number of organisations. As an outcome, the findings are based upon robust and big dataset with victim stays gathered from most of White-tailed Eagle areas inhabited in Scotland throughout the research study duration. It has actually been interesting to see how the diet plan differs in between specific areas and throughout areas. The vast array of victim products taped shows that the White-tailed Eagle is a versatile and opportunistic predator and scavenger, constant with findings from research studies somewhere else throughout the types vary in Europe.
“ E ilidh McNab, Development Officer for the Scottish Ornithologists’ Club who released the paper stated: “
The SOC is happy to support the publication of essential research study in Scottish ornithology through our quarterly journal, Scottish Birds. It is wonderful to see the return of such charming and renowned types as White-tailed Eagles to Scottish skies, and it is heartening that the population is broadening into locations where they have actually not been seen in over a century. This paper uses an interesting insight into the diet plan of our biggest bird of victim, and significantly contributes to the understanding base of their feeding behaviours in Scotland.” Duncan Orr-Ewing, Head of Species and Land Management at RSPB Scotland and member of the National Sea Eagle Stakeholder Group stated; “
This research study will be indispensable for an evidence-based method when preparing the next Sea Eagle Management Scheme and targeting of readily available resources to geographical locations where assistance is most required. We likewise hope that the outcomes of this research study will offer some peace of mind to famers and crofters in connection with their issues about animals predation and when keeping in mind the mainly natural diet plan of many reproducing White-tailed Eagles in Scotland.”