Capercaillie reinforcement feasibility study - Phase 1 report - July 2025

CAPER­CAIL­LIE REIN­FORCE­MENT FEAS­IB­IL­ITY STUDY – PHASE 1 REPORT June 2025

Pro­ject team:

Dr Mike Daniels, UHI Dr Ros Bryce, UHI Dr Helen Senn, RZSS Dav­id Barclay, RZSS Dr Simon Girl­ing, RZSS Dr Helen Taylor, RZSS Dr Alex Ball, RZSS Dr Erlend Nilsen, NINA Dr Duncan Hal­ley, NINA

This report sum­mar­ises the res­ults of a con­tract to:

1.1 Devel­op a set of pos­sible scen­ari­os for rein­for­cing the UK caper­cail­lie pop­u­la­tion and the poten­tial risks and bene­fits of each scenario.

1.2 Review and nar­row down the pos­sible scen­ari­os with a group of key stake­hold­ers in a work­shop con­vened by the Cairngorms Nation­al Park Authority.

1.3 Pro­duce a final report with recom­mend­a­tions regard­ing the scenario/​s that should be invest­ig­ated in more detail eco­lo­gic­ally, socially, prac­tic­ally and from a dis­ease perspective.

Tender back­ground

The Caper­cail­lie Emer­gency Plan recog­nises that if man­age­ment actions out­lined in the plan are insuf­fi­cient to reverse pop­u­la­tion declines, it may be neces­sary to rein­force the Scot­tish caper­cail­lie pop­u­la­tion with birds from out­side the UK. The Nation­al Spe­cies Rein­tro­duc­tion For­um advises that any rein­force­ment pro­ject (for any spe­cies) be care­fully coordin­ated with ongo­ing con­ser­va­tion efforts. To ensure a swift response should caper­cail­lie pop­u­la­tion declines con­tin­ue, this tender is the first step in explor­ing the feas­ib­il­ity of rein­for­cing the caper­cail­lie pop­u­la­tion with birds from Europe and per­form­ing exchanges with­in the Scot­tish caper­cail­lie population.

Report sec­tions

This report is in three sections:

PART A. Scen­ario ana­lys­is for caper­cail­lie con­ser­va­tion trans­lo­ca­tions based on a review of the lit­er­at­ure with input and dis­cus­sions among the pro­ject team

PART B: Report of stake­hold­er work­shop held on 22^nd May 2025 at the Cairngorms Nation­al Park Author­ity office Grant­own-on-Spey to dis­cuss the scen­ario ana­lys­is. The work­shop was atten­ded by 27 land man­agers and rep­res­ent­at­ives of landown­ers in caper­cail­lie SPAs with­in the Cairngorms Nation­al Park, mem­bers of the Caper­cail­lie Emer­gency Plan Pro­gramme Board, the Sci­entif­ic Advis­ory Group for the Caper­cail­lie Emer­gency Plan, the Roy Den­nis Wild­life Found­a­tion and mem­bers of the pro­ject team.

PART C: Recom­mend­a­tions and pro­posed next steps arising from the ana­lys­is and the workshop.

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PART A: Scen­ario ana­lys­is for caper­cail­lie con­ser­va­tion trans­lo­ca­tions in Scot­land 2025

Intro­duc­tion

The Cairngorms Caper­cail­lie Emer­gency Plan (Cairngorms Nation­al Park Author­ity and NatureScot, 2024) ​‘iden­ti­fies actions that will max­im­ise exist­ing oppor­tun­it­ies and address spe­cif­ic gaps across a range of inter­ven­tions to rap­idly bene­fit caper­cail­lie, from improv­ing hab­it­at to redu­cing the impact of pred­a­tion and dis­turb­ance at scale’. Sec­tion 8 of the Caper­cail­lie Emer­gency Plan also includes an action to eval­u­ate the feas­ib­il­ity of rein­for­cing the Scot­tish caper­cail­lie pop­u­la­tion by intro­du­cing birds from Europe and per­form­ing exchanges with­in the Scot­tish caper­cail­lie pop­u­la­tion. This report takes for­ward that objective.

In this risk / bene­fit ana­lys­is, we have examined pos­sible ways one might rein­force the caper­cail­lie pop­u­la­tion in Scot­land via trans­lo­ca­tions. The fol­low­ing ques­tions will also need to be con­sidered by the Pro­gramme Board and Sci­entif­ic Advis­ory Group for the Caper­cail­lie Emer­gency Plan, with input from stakeholders.

1. Would the cur­rent vis­ion* for the Caper­cail­lie Emer­gency Plan need to evolve to incor­por­ate the deliv­ery of a rein­force­ment pro­ject? For example, would we con­sider it a suc­cess to have the spe­cies main­tained in exist­ing loc­a­tions or should we be aim­ing for the spe­cies to become more wide­spread? A clas­sic spe­cies recov­ery vis­ion would be for the tar­get spe­cies: ​“to be secured and expand­ing in mul­tiple pop­u­la­tions of suit­able hab­it­at with lim­ited extern­al help/​with threats under­stood and managed/​in col­lab­or­a­tion with and bene­fit­ing loc­al people.”

• To improve caper­cail­lie breed­ing suc­cess and sur­viv­al across the core of the caper­cail­lie range in the Cairngorms Nation­al Park.

1. When would it be appro­pri­ate for rein­force­ment to be enacted? For example, should the decision be made while there is still a min­im­um viable population?

2. The Caper­cail­lie Emer­gency Plan is focused on deliv­er­ing imme­di­ate and tar­geted action to rap­idly bene­fit caper­cail­lie by expand­ing and improv­ing hab­it­at, redu­cing the impacts of pred­a­tion, remov­ing and mark­ing fences and redu­cing dis­turb­ance. In addi­tion, which threats would a rein­force­ment pro­ject seek to address?

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Rein­force­ment

Regard­ing the pur­poses of the trans­lo­ca­tion, we con­sider sev­er­al scen­ari­os here that meet the cri­ter­ia of a ​“rein­force­ment” of the Scot­tish caper­cail­lie pop­u­la­tion as a whole, depend­ing on what the vis­ion for the geo­graph­ic scope of this spe­cies is under a suc­cess­ful con­ser­va­tion out­come. These include:

• Rein­force­ment trans­lo­ca­tion – a trans­lo­ca­tion dir­ectly into an exist­ing pop­u­la­tion to bol­ster pop­u­la­tion size, genet­ic diversity, or both.

• Rein­tro­duc­tion trans­lo­ca­tion – a trans­lo­ca­tion into an area where the spe­cies exis­ted his­tor­ic­ally but has been extirp­ated. This action seeks to estab­lish a new pop­u­la­tion but, in doing so, still acts to rein­force the nation­al pop­u­la­tion as a whole. Bear in mind that any new pop­u­la­tion suc­cess­fully estab­lished could be man­aged as part of a nation­al meta- pop­u­la­tion with indi­vidu­als being moved between sub-pop­u­la­tions to pro­duce con­nectiv­ity if needed.

• Assisted col­on­isa­tion trans­lo­ca­tion – a trans­lo­ca­tion into an area where the spe­cies has not exis­ted pre­vi­ously, but where con­di­tions are felt to be suit­able and where the spe­cies will be able to ful­fil its eco­lo­gic­al role. Assisted col­on­isa­tions are vari­ously used to restore an eco­lo­gic­al func­tion to an area where it is miss­ing (e.g., Hansen et al., 2010) or to help a spe­cies out­run cli­mate change (e.g., Bouma et al., 2020). As with a rein­tro­duc­tion, assisted col­on­isa­tions with­in Scot­land would still act to rein­force the nation­al pop­u­la­tion as a whole and any new pop­u­la­tions estab­lished could be man­aged as part of a meta-population.

For more inform­a­tion on dif­fer­ent types of con­ser­va­tion trans­lo­ca­tions, please see the glob­al and nation­al guidelines on this top­ic (Inter­na­tion­al Uni­on for the Con­ser­va­tion of Nature (IUCN) Spe­cies Sur­viv­al Com­mis­sion, 2013; Nation­al Spe­cies Rein­tro­duc­tion For­um, 2014).

Note: The scen­ari­os presen­ted in this doc­u­ment are not mutu­ally exclus­ive. For example, depend­ing on the pur­pose of the trans­lo­ca­tion, a mix of source pop­u­la­tions could be selec­ted, mul­tiple types of release site could be tri­alled, and a mix of release tech­niques could be used. This was the approach taken by the Pol­ish EULife pro­ject where a total of 406 caper­cail­lie were released from three Pol­ish breed­ing centres, plus trans­lo­ca­tions from Scand­inavia and Rus­sia (Kobiel­ski et al., 2019). See Fig­ure 1 for a schem­at­ic of options and decision points con­sidered in this doc­u­ment for caper­cail­lie trans­lo­ca­tions in Scotland.

Fig­ure 1: Decision tree depict­ing the vari­ous con­ser­va­tion trans­lo­ca­tion scen­ari­os and strategies con­sidered in this doc­u­ment for rein­for­cing the Scot­tish caper­cail­lie. Orange lines = ex-situ breed­ing and release route. Blue lines = wild to wild trans­lo­ca­tion. As noted in the text, scen­ari­os and strategies are not mutu­ally exclus­ive and could be used in com­bin­a­tion to achieve con­ser­va­tion goals.

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Baseline decision: what type of trans­lo­ca­tion is required?

Decision 1: Where to release

Release into exist­ing strong­hold pop­u­la­tion in Strathspey

Release into low dens­ity frag­men­ted pop­u­la­tions (e.g., Deeside)

Release into cur­rently empty areas of known nat­ur­al range

Release into new area(s) out­side of known nat­ur­al range

Decision 2: a) Wild to wild or ex-situ breed­ing for release and b) what life stage to bring in

Birds and/​or eggs

Con­ser­va­tion breed­ing facility

Bring in indi­vidu­als from over­seas Use indi­vidu­als from Scotland

Decision 3: Where to source individuals

Birds from sim­il­ar area to ori­gin­al Scot­tish rein­tro­duc­tion (i.e., Sweden and Norway)

Birds from dif­fer­ent area to ori­gin­al Scot­tish rein­tro­duc­tion (i.e., out­side Sweden and Norway)

Birds from low dens­ity, rem­nant pop­u­la­tions (e.g., Deeside)

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Birds from high­er dens­ity strong­hold pop­u­la­tion (Strath­spey)

Decision 1 — Where to release birds?

Over­all con­sid­er­a­tions – Trans­lo­ca­tions do not exist in a vacu­um and, wherever the birds are released, it is neces­sary to look at all factors such as hab­it­at qual­ity, dis­turb­ance, pred­a­tion etc. which could cause rein­tro­duc­tion failure

There are dif­fer­ent cost implic­a­tions depend­ing on the type of trans­lo­ca­tion being under­taken. For example, a rel­at­ively small num­ber of birds into an exist­ing pop­u­la­tion for a rein­force­ment versus estab­lish­ing a new pop­u­la­tion. A full-scale trans­lo­ca­tion rein­tro­duc­tion pro­gramme for caper­cail­lie with a mixed strategy of releas­ing wild and cap­tive-bred birds is likely to cost mil­lions of pounds.

Option Bene­fits Risks Into exist­ing strong­hold pop­u­la­tion in Strath­spey (rein­force­ment) With­in the Cairngorms Nation­al Park Cli­mate may become unsuit­able, neg­at­ing any efforts to rein­force this population.

Inab­il­ity to upscale meas­ures piloted in Cairngorms Caper­cail­lie Pro­ject to address disturbance.

If pop­u­la­tion in strong­hold is in decline at time of rein­force­ment, it is pos­sible the agents of this decline have not been addressed, increas­ing the num­ber of birds that would need to be released to render this approach suc­cess­ful. Know­ledge Gaps

Pop­u­la­tion viab­il­ity ana­lys­is required to assess num­ber of birds needed to res­ult in a use­ful improve­ment in genet­ic diversity.

Note: Even a rein­force­ment release may require hun­dreds of birds (Kobiel­ski et al., 2019).

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Into low dens­ity, frag­men­ted pop­u­la­tions such as Deeside (rein­force­ment)

Into pre­vi­ously occu­pied range where spe­cies has been extirp­ated (rein­tro­duc­tion)

Some sites with­in Nation­al Park

Oppor­tun­ity to identi­fy site with bet­ter con­di­tions than cur­rent range.

Some sites with­in Nation­al Park — there are areas of estab­lished wood­land with­in the Nation­al Park that do not cur­rently hold caper­cail­lie (Cairngorms Nation­al Park Author­ity, 2015 Fig­ure 2) and areas that could be estab­lished with hab­it­at man­age­ment (Cairngorms Nation­al Park Author­ity, 2015 Fig­ures 3 – 5).

Oppor­tun­ity to increase extent of occur­rence and area of occu­pancy while creating

Cli­mate may become unsuit­able, neg­at­ing any efforts to rein­force this population.

If pop­u­la­tion in site is in decline at time of rein­force­ment, it is pos­sible the agents of this decline have not been addressed, increas­ing the num­ber of birds that would need to be released to render this approach successful.

Cli­mate may become unsuit­able, neg­at­ing any efforts to rein­tro­duce this population.

Do we have a full under­stand­ing of why the spe­cies was extirp­ated from area?

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Into new areas out­side the known nat­ur­al range of the spe­cies in Scot­land (assisted colonisation)

insur­ance pop­u­la­tions should cur­rent strong­hold and/​or low- dens­ity Scot­tish pop­u­la­tions decline/​disappear – spread the risk.

Oppor­tun­ity to identi­fy site with bet­ter con­di­tions than cur­rent range.

Oppor­tun­ity to identi­fy site with more long-term cli­mate suit­ab­il­ity for the spe­cies based on cli­mate change pre­dic­tions – could address chal­lenges with poor rain­fall and inver­teb­rate avail­ab­il­ity iden­ti­fied in Bel­gi­um and Neth­er­lands (Hilde et al., 2024).

Oppor­tun­ity to increase extent of occur­rence and area of occu­pancy while cre­at­ing insur­ance pop­u­la­tions should cur­rent strong­hold and/​or low- dens­ity Scot­tish pop­u­la­tions decline/​disappear – spread the risk.

Sites likely to be out­with Nation­al Park — addi­tion­al part­ner­ships required. Pos­sibly dif­fi­cult to jus­ti­fy Park Author­ity sup­port for work unless a clear link is estab­lished to sup­port­ing pop­u­la­tions in the Nation­al Park.

What is our con­fid­ence in pre­dict­ing suit­able hab­it­at for caper­cail­lie both at present time and under con­di­tions pre­dicted under cli­mate change? Is there hab­it­at con­sidered more suit­able than that in the known/​historic range?

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Decision 2 – a) Wild to wild or con­ser­va­tion breed­ing and release, and b) what life stage to bring in?

Over­all con­sid­er­a­tions – it is likely that estab­lish­ing suc­cess­ful, self-sus­tain­ing pop­u­la­tions of caper­cail­lie in Scot­land (or even rein­for­cing cur­rent pop­u­la­tions) will require the release of hun­dreds of birds over sev­er­al years.

It is key to remem­ber that in the event that an ex-situ con­ser­va­tion breed­ing pro­gramme is com­mis­sioned, it would likely take sev­er­al years before the pro­gramme was ready to release birds.

Option Bene­fits Risks Wild to wild trans­lo­ca­tion of birds Pos­sible to cap­ture females post- cop­u­la­tion, but before egg lay­ing — could have a clutch almost Large num­bers of birds likely required to be trans­por­ted. From (World Pheas­ant Asso­ci­ation and IUCN/SSC Rein­tro­duc­tion imme­di­ately (Hilde et al., 2024). But if eggs laid in trans­port­a­tion — Spe­cial­ist Group, 2009): ​“when have to be reared in a breed­ing centre (see risks). Birds seem to sur­vive trans­port well. Of a total of 519 birds cap­tured and trans­por­ted from Sweden, there have been nine fatal­it­ies dur­ing trans­port­a­tion or just after release (with­in two weeks) (=1.7% of birds) (Hilde et al., 2024). Lower cost than build­ing breed­ing centres but, as noted above and to right, some kind of incub­a­tion and rear­ing facil­ity may still be

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Know­ledge Gaps

con­sid­er­ing the rein­tro­duc­tion of caper­cail­lie to south­ern Scot­land, sim­u­la­tions estim­ated that a min­im­um of 60 indi­vidu­als would be required across 5000 hec­tares of hab­it­at in order for the pop­u­la­tion to have a >0.95 prob­ab­il­ity of sur­viv­ing for 50 years. Sup­ple­ment­a­tion of pop­u­la­tions with two unre­lated indi­vidu­als every five years reduced the min­im­um viable pop­u­la­tion to ten indi­vidu­als (Mar­shall and Edwards-Jones, 1998). Altern­at­ively, col­la­tion and ana­lys­is of numer­ous grouse re

required in addi­tion to suit­able quar­ant­ine facilities.

Oppor­tun­ity to col­lect data and learn more about the spe­cies in Scot­land using radio tag­ging of released birds.

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intro­duc­tion pro­jects using cap­tive-reared birds, sug­gests that annu­al releases of at least 30 birds are neces­sary for at least six years, in order to estab­lish a pop­u­la­tion with 50% prob­ab­il­ity of sur­viv­al and repro­duc­tion (Seiler et al., 2000).”

It may only be pos­sible to source wild birds in rel­at­ively small num­bers each year. From NINA 2024 report for Swedish EPΑ: ​“Mean num­bers of cap­tures per year are 19 for caper­cail­lie” (Hilde et al., 2024).

For cer­tain source pop­u­la­tions, it may not be advis­able to take large num­bers of birds for trans­lo­ca­tions as they would not be able to with­stand the har­vest of large num­bers of individuals.

Small-scale incub­a­tion and rear­ing facil­ity may still be required if females lay eggs in trans­it. Could be neg­ated by trans­port­ing females out­side breed­ing sea­son but would also lose poten­tial bene­fit of females lay­ing eggs on arrival.

Wild to wild trans­lo­ca­tion eggs Min­im­al hand­ling of birds required all hand­ling done at egg stage.

Poten­tially less stress­ful for indi­vidu­als to be trans­por­ted as eggs than as birds.

Poten­tially less impact­ful on source pop­u­la­tion if females are able to re-lay after eggs have been taken.

Nov­el approach and thus untri­alled (as far as we can tell).

Has to be into exist­ing pop­u­la­tions so that eggs can be placed in nests of wild caper­cail­lie — can­not be used to found new population.

If not enough nests are loc­ated to place all eggs, it could lead to need for unplanned ex-situ incub­a­tion and rearing.

It is unlikely that eggs from the wild would be allowed to be trans­ferred into Scot­land. If they were, chicks would need to be held in quar­ant­ine for at least three weeks post-hatch­ing to allow for addi­tion­al dis­ease screening.

Tim­ing of egg trans­lo­ca­tion and nest­ing birds in Scot­land would need to be very precise.

Females could aban­don nests if dis­turbed by egg place­ment as hap­pens in oth­er bird spe­cies (e.g., Car­ney and Syde­man, 1999).

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How easy is it to trans­port fer­tile caper­cail­lie eggs and have them remain viable?

Feas­ib­il­ity of put­ting eggs under wild black grouse hens for fos­ter­ing. This was done his­tor­ic­ally in the suc­cess­ful rein­tro­duc­tion of caper­cail­lie to Scot­land, but at a time where black grouse were more numer­ous. There are also con­cerns regard­ing fos­ter­ing of caper­cail­lie by black grouse, lead­ing to a tend­ency to hybrid­isa­tion between the two species.

Ex-situ breed­ing and release birds Poten­tial for a con­tinu­ous sup­ply of birds.

Facil­ity could double as a quar­ant­ine facil­ity and could also have an egg incub­a­tion facility.

May require few­er birds to be sourced from wild as intent would be to breed large num­bers of birds for release (but see genet­ic risk to right).

Hav­ing anim­als in a breed­ing facil­ity provides research oppor­tun­it­ies regard­ing diet and beha­viour that could enhance rein­tro­duc­tion efforts.

Oppor­tun­ity to col­lect data and learn more about the spe­cies in Scot­land using radio tag­ging of released birds.

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Dif­fi­cult to mon­it­or birds that have hatched out — can­not tag pre- hatch and would not be able to identi­fy which bird came out of which egg.

Risk of inbreed­ing and loss of genet­ic diversity in cap­tive breed­ing pop­u­la­tion if not man­aged effect­ively. Addi­tion­al birds may be required to be intro­duced into ex-situ pop­u­la­tion depend­ing on suc­cess and genet­ic mix of founders.

Most cap­tive breed­ing and release pro­gramme for caper­cail­lie have failed. This is thought to have been due to a lack of pred­at­or avoid­ant beha­viour and changes in gut mor­pho­logy in an ex-situ set­ting (D Merta et al., 2015).

Rel­at­ively large amount of space needed to reduce ant­ag­on­ist­ic con­tact between nest­ing females and increase nest­ing suc­cess. From (Rosen­ber­ger et al., 2020): it is sug­ges­ted that ant­ag­on­ist­ic beha­viour between females

No ex-situ caper­cail­lie in the UK cur­rently, but there are private own­ers in the UK — the status of this privately held ex-situ pop­u­la­tion is unknow so fur­ther research is needed.

There is seem­ingly a well- estab­lished ex-situ breed­ing pro­gramme for caper­cail­lie in Europe, but more inform­a­tion is required on cur­rent suc­cesses of ex-situ caper­cail­lie rear­ing meth­ods as, his­tor­ic­ally, suc­cess­ful par­ent-rear­ing with this spe­cies ex-situ was very rare. There is some evid­ence from France (pers. comm. to D Barclay) that recent suc­cesses have been achieved with caper­cail­lie hus­bandry and rearing.

Use tech­niques from the EULIFE- fun­ded pro­ject in Poland – ​“Born to be Free” meth­ods (Krzy­wiński et al., 2013) where chicks are reared in semi-liberty by their moth­er and released next to their mother’s pen, which show longer post-release sur­viv­al times vs. tra­di­tion­al rear­ing and non- moth­er-assisted release meth­ods (Dorota Merta et al., 2015). This is thought to be due to released juven­iles roam­ing less widely and being able to heed their mother’s warn­ings re: pred­a­tion. ​“Born to be Free” meth­od birds have also been shown to have lower endo- para­site bur­dens (Sokół and Pluta, 2022).

Great­er con­trol re: selec­tion of anim­als for release (e.g., age and relatedness).

Poten­tial to double-clutch birds to build up a lar­ger cap­tive pop­u­la­tion quicker.

Could still facil­it­ate eggs being placed under wild birds if this approach was felt to be appropriate/​useful.

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observed even at nest­ing dens­it­ies of one bird per 132m². ​“Born to be Free” meth­od requires release avi­ar­ies to be con­struc­ted in the release site.

Ex-situ breed­ing and release eggs After first clutch of impor­ted eggs under hens are hatched, this allows for pro­mo­tion of double-clutch­ing by female caper­cail­lie from second sea­son onwards, as the first clutch can be reared by broody hens while the female caper­cail­lie incub­ates a second clutch — if suc­cess­ful, allows for up to double ex-situ pop­u­la­tion growth rate.

This has been done suc­cess­fully at RZSS High­land Wild­life Park in the past.

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Use of domest­ic­ated hens could intro­duce addi­tion­al dis­ease risks if robust disease/​biosecurity con­trols are not in place.

May lead to reduced pred­at­or avoid­ance beha­viour in released animals.

Requires con­struc­tion of a rear­ing facility.

If used as only approach it may lead to reduced skills/​expertise with caper­cail­lie par­ent rearing.

Increases hus­bandry require­ment and hold­ing space re: num­ber of anim­als (caper­cail­lie and domest­ic hens).

Need to under­stand the impact of poten­tial foster rear­ing vs wild beha­viours e.g., pred­at­or avoid­ance and mate seeking/​reproductive behaviour.

Decision 3 – Where should birds be sourced from?

Over­all con­sid­er­a­tions – The latest genet­ic data (Ball and Ritch­ie-Park­er, 2023) sug­gest that, when com­pared to oth­er pop­u­la­tions in Europe, Scot­tish caper­cail­lie have rel­at­ively low genet­ic diversity. Inter­est­ingly, genet­ic diversity with­in the Scot­tish pop­u­la­tion has not changed over the 20^th cen­tury, sug­gest­ing the pop­u­la­tion has not exper­i­enced a genet­ic bot­tle­neck in that time. With­in the Scot­tish pop­u­la­tions, Aber­nethy stands out as a reser­voir of genet­ic lines that are not found else­where in Scot­land at high fre­quency. The genet­ic makeup of Scot­tish caper­cail­lie reflects their Scand­inavi­an ori­gins, with Scot­tish birds being most genet­ic­ally sim­il­ar to those from Sweden and Nor­way. Out of eight pop­u­la­tions examined in detail (Scot­land, Sweden, Fin­land, Ger­many, Aus­tria, Nor­way, Poland, and France) the Scot­tish pop­u­la­tion was most dis­tinct from Fin­land, (with the excep­tion of France, which is, itself, genet­ic­ally isol­ated and has low vari­ab­il­ity).. Fin­land also has some of the highest genet­ic diversity of the pop­u­la­tions examined, both in mito­chon­dri­al and nuc­le­ar DNA. While there are not offi­cially any ex-situ caper­cail­lie in the UK cur­rently, there are private own­ers in the UK – the status of this privately held ex-situ pop­u­la­tion is unknow so fur­ther research is needed as to how genet­ic­ally dis­tinct they may be from the Scot­tish pop­u­la­tion and oth­er pop­u­la­tions in Europe.

Option Bene­fits Risks Over­seas (over­all) Oppor­tun­ity to intro­duce nov­el genet­ic vari­ation not cur­rently found in Scot­tish pop­u­la­tion, improv­ing resi­li­ence to chan­ging cir­cum­stances and redu­cing risk of inbreeding.

Oppor­tun­ity to source birds from pop­u­la­tions that are appar­ently robust to har­vest­ing for trans­lo­ca­tion (Hilde et al., 2024).

Poten­tial to explore both in-situ and ex-situ sources of birds giv­en the breed­ing centres cur­rently estab­lished in loc­a­tions like Poland, as well as import­ing of

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Longer trans­port dis­tances great­er risk of stress to animals.

Longer quar­ant­ine require­ments both before and after import, with addi­tion­al test­ing required for avi­an influ­enza and para­myx­ovir­us both before and after import.

Depend­ing on pur­pose of trans­lo­ca­tion, mul­tiple imports in suc­cess­ive years may be required each import will require tem­por­ary hold­ing for quar­ant­ine and the test­ing described above. Know­ledge Gaps

Over­seas, from sim­il­ar pop­u­la­tions as pre­vi­ous Scot­tish rein­tro­duc­tion (i.e., Sweden)

eggs and/​or semen in addi­tion to live birds. Estab­lished and well-run pro­gramme for cap­ture and Not a risk but note that all the pro­jects receiv­ing birds from trans­port of birds already exists in Sweden must report their Sweden. Birds mov­ing to (cur­rently) sim­il­ar cli­mate as source pop­u­la­tion. Cur­rent Scot­tish pop­u­la­tion does not rep­res­ent all known genet­ic vari­ation in Swedish pop­u­la­tion (Ball and Ritch­ie-Park­er, 2023), thus bring­ing anim­als in from Sweden could intro­duce nov­el genet­ic vari­ation to the Scot­tish pop­u­la­tion (but see risks). Poten­tial exist­ing col­lab­or­a­tions between Scot­tish organ­isa­tions and con­ser­va­tion mon­it­or­ing res­ults annu­ally to get a per­mit for con­tinu­ing cap­tures, includ­ing sur­viv­al dur­ing the first months after release and repro­duc­tion the fol­low­ing sea­son. ​“Start­ing in 2023, the Swedish EPA will request a PVA for pro­jects apply­ing to cap­ture caper­cail­lie in Sweden.” (Hilde et al., 2024). Loc­al com­munit­ies not always in favour of birds being removed – may attempt to sab­ot­age cap­ture (Hilde et al., 2024). Risk would be for sup­pli­er (e.g., NINA) to bear, but could impact num­bers of projects/​facilities in Sweden (e.g., birds sup­plied to Scot­land from Nor­dens Ark) that could poten­tially assist with tem­por­ary hold­ing, quar­ant­ine, addi­tion­al ex- situ breed­ing etc.

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Sweden.

Unlikely to improve genet­ic diversity giv­en sim­il­ar­ity of cur­rent Scot­tish pop­u­la­tion to Scand­inavi­an stock (Ball and

Over­seas, from dif­fer­ent pop­u­la­tions to pre­vi­ous Scot­tish pop­u­la­tion founders

Entirely new genet­ic diversity if new source pop­u­la­tion selec­ted based on latest genet­ic data (Ball and Ritch­ie-Park­er, 2023). E.g., Fin­land could be a suit­able source pop­u­la­tion to enhance genet­ic diversity in Scot­land. Good chance of increas­ing resi­li­ence against chan­ging cir­cum­stances (e.g., dis­ease and cli­mate change) and redu­cing risks of inbreeding.

Depend­ing on source pop­u­la­tion selec­ted, birds mov­ing to (cur­rently) sim­il­ar cli­mate as source population.

Some con­tacts exist between organ­isa­tions in Scot­land and the European ex-situ breed­ing pro­gramme plus oth­er breed­ing for release pro­jects for the spe­cies (e.g., in North­ern Spain) – these could act as addi­tion­al sources of birds from oth­er genet­ic stock and geo­graph­ic origin.

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Ritch­ie-Park­er, 2023) (but see benefits).

Could res­ult in longer trans­port dis­tances and travel times than birds from Sweden and asso­ci­ated risk and increased stress to birds being transported.

A lot of main­land European pop­u­la­tions are frag­men­ted and/​or in decline (e.g., Spain, France, Ger­many) (Coppes et al., 2015; Gil et al., 2020; Jahren et al., 2016; Mikoláš et al., 2015) and so, for some pop­u­la­tions, it may be dif­fi­cult to get per­mis­sion to take birds to Scot­land if there is a poten­tial for a neg­at­ive effect on donor population.

Avail­ab­il­ity of birds from coun­tries out­side Sweden or Norway.

Under­stand­ing what cli­mat­ic changes caper­cail­lie in oth­er loc­a­tions are sub­ject to and how they are respond­ing would help select a source pop­u­la­tion that is best adap­ted to the cur­rent and pre­dicted Scot­tish climate.

Need to invest­ig­ate vari­ous dif­fer­ent licens­ing pro­cesses, gov­ern­ment approv­al from addi­tion­al source coun­tries as these could vary from coun­try to country.

There is some evid­ence that caper­cail­lie in dif­fer­ent biore­gions have dif­fer­ent diets (Gonza­lez et al., 2012), which could affect the suit­ab­il­ity of birds from cer­tain pop­u­la­tions for life in Scot­land. More under­stand­ing of this is required.

With­in Scot­land (over­all)

With­in Scot­land, col­lect up birds from low dens­ity pop­u­la­tions (e.g., Deeside)

If cli­mate change is thought to be a threat to Scot­tish caper­cail­lie pop­u­la­tion, sourcing birds from a cli­mate more sim­il­ar to what Scot­land has/​is shifted/​shifting towards could cre­ate more resi­li­ence to this threat.

Short­er quar­ant­ine require­ments (though note, this is depend­ent on the avi­an influ­enza situ­ation at any giv­en time).

Likely short­er timeline for trans­lo­cat­ing birds.

Oppor­tun­ity to use birds from extremely low-dens­ity pop­u­la­tions that may not oth­er­wise have the chance to breed and con­trib­ute to the Scot­tish pop­u­la­tion, by mov­ing them into high­er dens­ity areas.

Rel­at­ively low-cost meth­od to boost num­bers and (if dens­ity depend­ent) repro­duct­ive suc­cess in strong­hold pop­u­la­tions with a high­er long-term sur­viv­al prob­ab­il­ity in the first place,

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No new genet­ic diversity intro­duced (improved con­nectiv­ity and lar­ger pop­u­la­tion sizes could slow the loss of genet­ic diversity and reduce inbreed­ing, but this loss will still occur).

Could be per­ceived as giv­ing up on cer­tain populations/​forcing their extirp­a­tion if com­mu­nic­a­tions and engage­ment around decision not very care­fully handled.

May require robust pop­u­la­tion estim­ates of all sub-pop­u­la­tions in Scot­land to enable evid­ence- based decisions.

A PVA ana­lys­is might help untangle exactly how bene­fi­cial (if at all) this strategy might be.

There are few­er data on genet­ic diversity of caper­cail­lie in these pop­u­la­tions due to the under­stand­ably low sample sizes avail­able. For example, pre­vi­ous stud­ies of birds from Ross and Cro­marty have iden­ti­fied an There is no ​“unique” genet­ic vari­ation in the samples from any of the low-dens­ity pop­u­la­tions (Ball and Ritch­ie-Park­er, 2023), so this move would not add any­thing mtDNA hap­lo­type not seen in the new (but see bene­fits and unknowns).

most recent study (Ball and Ritch­ie-Park­er, 2023; Segel­bach­er and Piert­ney, 2007). This variation

With­in Scot­land, from with­in strong­hold pop­u­la­tion in Strathspey

min­im­ising chance of spe­cies extinc­tion in Scotland.

While not adding any new genet­ic mater­i­al, adding in indi­vidu­als and (hope­fully) boost­ing the size of the breed­ing pop­u­la­tion could act to slow the loss of genet­ic diversity from the population.

Oppor­tun­ity to intro­duce genet­ic diversity from Aber­nethy, which is unique with­in Scot­land (Ball and Ritch­ie-Park­er, 2023), into oth­er Scot­tish pop­u­la­tions. This would strengthen genet­ic resi­li­ence across the board if trans­lo­cated birds breed with recip­i­ent pop­u­la­tion indi­vidu­als and make it less likely that these genet­ic vari­ants will be lost if any­thing hap­pens to the Aber­nethy population.

Oppor­tun­ity to enhance and retain pop­u­la­tions out­side of the cur­rent strong­hold in Strathspey.

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If inbreed­ing has occurred in low dens­ity pop­u­la­tions, then it may have led to inbreed­ing depres­sion, which could lead to neg­at­ive effects on sur­viv­al and/​or reproduction.

Strong­hold pop­u­la­tion in Strath­spey may not be able to with­stand har­vest of num­ber of indi­vidu­als required to max­im­ise chance of sur­viv­al and repro­duc­tion in recip­i­ent population/​breeding facility.

could have been lost, or still be present and just not sampled.

Ref­er­ences

Ball, A., Ritch­ie-Park­er, H., 2023. Ana­lys­ing the genet­ic diversity of the caper­cail­lie pop­u­la­tion in the Cairngorms Nation­al Park.

Bam­ber, J.A., Kort­land, K., Suth­er­land, C., Payo-Payo, A., Lambin, X., 2024. Eval­u­at­ing diver­sion­ary feed­ing as a meth­od to resolve con­ser­va­tion con­flicts in a recov­er­ing eco­sys­tem. Journ­al of Applied Eco­logy 61, 1968 – 1978. https://doi.org/https://doi.org/10.1111/1365 – 2664.14693

Bouma, A., Kuch­ling, G., Zhai, S., Mitchell, N., 2020. Assisted col­on­isa­tion tri­als for the west­ern swamp turtle show that juven­iles can grow in cool­er and wet­ter cli­mates. Endanger Spe­cies Res 43. https://​doi​.org/​1​0​.​3​3​5​4​/​e​s​r​01053

Cairngorms Nation­al Park Author­ity, 2015. Cairngorms Caper­cail­lie Frame­work Phase 1 Report.

Cairngorms Nation­al Park Author­ity, NatureScot, 2024. Caper­cail­lie Emer­gency Plan 2025-

1. Grant­own-on-Spey.

Car­ney, K.M., Syde­man, W.J., 1999. A Review of Human Dis­turb­ance Effects on Nest­ing Colo­ni­al Water­birds. Water­birds: The Inter­na­tion­al Journ­al of Water­bird Bio­logy 22, 68–

1. https://​doi​.org/​1​0​.​2​3​0​7​/​1​5​21995

Coppes, J., Kochs, M., Ehr­lach­er, J., Suchant, R., Braunisch, V., 2015. The chal­lenge of cre­at­ing a large-scale caper­cail­lie dis­tri­bu­tion map. Grouse News 50, 21 – 23.

Finne, M.H., Kris­ti­ansen, P., Rol­stad, J., Wegge, P., 2019. Diver­sion­ary feed­ing of red fox in spring increased pro­ductiv­ity of forest grouse in south­east Nor­way. Wild­life Biol 2019, wlb.00492. https://doi.org/https://doi.org/10.2981/wlb.00492

Gil, J.A., Gómez-Ser­rano, M.Á., López-López, P., 2020. Pop­u­la­tion Decline of the Caper­cail­lie Tet­rao urogal­lus aquit­an­i­cus in the Cent­ral Pyren­ees. Ardeola 67, 285 – 306. https://​doi​.org/​1​0​.​1​3​1​5​7​/​a​r​l​a​.​6​7​.​2​.​2​0​2​0.ra4

Gonza­lez, M.A., Olea, P.P., Mateo-Tomas, P., Gar­cia-Tejero, S., De Frutos, Á., Robles, L., Purroy, F.J., Ena, V., 2012. Hab­it­at selec­tion and diet of West­ern Caper­cail­lie Tet­rao urogal­lus in an atyp­ic­al biogeo­graph­ic­al region. Ibis 154, 260 – 272. https://doi.org/https://doi.org/10.1111/j.1474 – 919X.2012.01217.x

Hansen, D.M., Don­lan, C.J., Grif­fiths, C.J., Camp­bell, K.J., 2010. Eco­lo­gic­al his­tory and lat­ent con­ser­va­tion poten­tial: large and giant tor­toises as a mod­el for tax­on sub­sti­tu­tions. Eco­graphy 33, 272 – 284. https://doi.org/https://doi.org/10.1111/j.1600- 0587.2010.06305.x

Hilde, C.H., Dehnhard, N., Nilsen, E.B., 2024. Trans­lo­ca­tion of caper­cail­lie and black grouse from Sweden to cent­ral Europe: An eval­u­ation of ongo­ing trans­lo­ca­tion pro­jects. Bromma, Sweden.

IUCN Spe­cies Sur­viv­al Com­mis­sion, 2013. Guidelines for Rein­tro­duc­tions and Oth­er Con­ser­va­tion Trans­lo­ca­tions. IUCN Spe­cies Sur­viv­al Com­mis­sion, Gland, Switzerland.

Jahren, T., Stor­aas, T., Wil­l­eb­rand, T., Foss­land Moa, P., Hagen, B.-R., 2016. Declin­ing repro­duct­ive out­put in caper­cail­lie and black grouse – 16 coun­tries and 80 years. Anim­al Bio­logy 66, 363 – 400. https://doi.org/https://doi.org/10.1163/15707563 – 00002514

Kobiel­ski, J., Ławreszuk, D., Merta, D., 2019. After-LIFE Con­ser­va­tion Plan: Act­ive pro­tec­tion of the low­land pop­u­la­tions of caper­cail­lie (Tet­rao urogal­lus L.) in the Bory Dol­nośląskie Forest and Augus­towska Primev­al Forest.

Krzy­wiński, A., Keller, M., Kobus, A., 2013. ​“Born to be free” — an innov­at­ory meth­od of resti­tu­tion and pro­tec­tion of endangered and isol­ated grouse pop­u­la­tions (Tet­raonid­ae). Vogel­welt 134.

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Mar­shall, K., Edwards-Jones, G., 1998. Rein­tro­du­cing caper­cail­lie (Tet­rao urogal­lus) into south­ern Scot­land: iden­ti­fic­a­tion of min­im­um viable pop­u­la­tions at poten­tial release sites. Biod­ivers Con­serv 7, 275 – 296. https://​doi​.org/​1​0​.​1​0​2​3​/​A​:​1​0​0​8​8​4​4​7​26747

Merta, Dorota, Kobiel­ski, J., Krzy­wiński, A., Theuerkauf, J., Gula, R., 2015. A new moth­er- assisted rear­ing and release tech­nique (“born to be free”) reduces the explor­at­ory move­ments and increases sur­viv­al of young caper­cail­lies. Eur J Wildl Res 61,299 – 302. https://doi.org/10.1007/s10344-015‑0899‑3

Merta, D, Zawadzka, D., Krzy­w­in­ski, A., 2015. Effect­ive­ness of caper­cail­lie (Tet­rao urogal­lus) rein­tro­duc­tion pro­jects in Europe. Syl­wan 159, 863 – 871