Radio-tracking Case Study

radio tracking 0Photo courtesy of Davorin Tome

Whinchats, Saxicola rubetra, Slovenia
Survival & predator avoidance in the post-fledgling period

It is well known that European populations of farmland birds, are decreasing due to modern agricultural practices. The ‘stay-and-hide’ strategy for predator avoidance is ineffective against agricultural mowing machinery.

In the study area, Ljubljansko barje, Slovenia, the Whinchat population has decreased by 50% in the last 10 years. Mortality caused by earlier mowing is highly responsible for this decline, after habitat change and reduced invertebrate food.Survival and behavioural data in juvenile Whinchats after fledgling is limited so the aims of this study were to…


i) Present mortality & survival rates without mowing interference

ii) Describe a behaviour in the first days after leaving the nest, as understanding of predator-avoidance strategy of fledglings is crucial for planning an efficient conservation measure.


Equipment Used


Biotrack PIP3 backpack radio transmitters - 0.6g weight, 20 days expected battery lifespan. Over 3 years, 74 juvenile birds were tagged.
Biotrack Sika Manual tracking receiver - 138.000—173.999 MHz
Flexible 3-element Yagi antenna - 142 MHz

Insights


1. Chicks started leaving the nest at 13 days of age. There is a steep decline in survival rate between age 12 days and 16 days (from 1.0 down to 0.7).

2. Predation was the cause of 18 out of 21 mortality events (carcasses located by radio tracking).

3. There is a 50% probability a 20 day old Whinchat will stay still and not escape when a threat approaches, reducing to 20% by 22 days age, when the main response is to fly away instead.

4. To reduce threats to fledglings from mowing, it is therefore recommended that mowing be postponed 10 days more, to when most fledglings will able to avoid an approaching mowing threat, rather than when 80%

 

radio tracking 1 radio tracking 2

Fig. 1 Medium distances of young Whinchats from the nest (bars),
with minimum and maximum lines also shown. Arrows indicate the
period when birds were leaving the nest; numbers at the top are
sample sizes

 

 

Fig. 2 Cumulative survival probability of young Whinchats versus
age, calculated using Kaplan -Meier estimates (N = 74). Vertical
lines
are 95% confidence intervals, arrows indicate the period when
birds are leaving the nests

In Conclusion


Radio tracking fledglings has shown us that the current
mowing postponement until fledging is not a sufficient
measure to halt population decline for Whinchats. We
suggest at least 10 more days, when the majority of
fledglings will have changed from the ‘stay and hide’
to the ‘escaping through flight’ strategy.


This case study is a summary of: Davorin, T., Denac, D.
(2011), Survival and development of predator avoidance
in the post-fledging period of the Whinchat (Saxicola
rubetra): consequences for conservation measures.
Journal of Ornithology. doi: 10.1007/s10336-011-0713-2.


Many thanks to the authors for their permission and
assistance in the creation of this case study.


radio tracking 3

 

 

Fig. 3 Predicted escape probabilities of Whinchat fledglings in
relation to their age. Left solid line (a) represents the probability
that fledglings will escape from the approaching threat irrespective of
the distance; right solid line (b) represents the probability that they
will escape when the threat is at a distance of 5 m or more. Dashed
lines show the 95% confidence intervals of the predicted values

To the whole team at Sirtrack,

I wanted to personally send you our 2011 Thank you video which highlights the achievements we have made together for the people and animals at N/a’an ku sê. Thank you for everything you’ve done in 2011 to help make this happen – from sponsoring collars to help us safely release threatened cheetahs and sharing our news and stories with your clients - here’s to a successful 2012 together!

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Just to let you know, our Wild Animal Orphans TV series premieres on Tuesday 6th March on Animal Planet across Africa, as well as in Holland, Belgium, Finland, Norway, Denmark, Sweden, Greece, Croatia, Hungary, Turkey, many other European countries, across the Middle East and Russia. I’m currently seeing how I can get you a copy of Groen so you can see the exposure you got. I might have to wait until all 13 episodes of WAO is aired before sending to you, hope that’s ok.

With best wishes,

Lucy Hale

Fundraising and Marketing Manager

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www.naankuse.com

TTo the whole team at Sirtrack,

I wanted to personally send you our 2011 Thank you video which highlights the achievements we have made together for the people and animals at N/a’an ku sê. Thank you for everything you’ve done in 2011 to help make this happen – from sponsoring collars to help us safely release threatened cheetahs and sharing our news and stories with your clients - here’s to a successful 2012 together!

Please enjoy it and feel proud of the difference you’ve made:

http://www.youtube.com/watch?v=k-wHpBVytrI&feature=plcp&context=C300d1dbUDOEgsToPDskK2BT7ILrG91-MWctn4Pyx9

Just to let you know, our Wild Animal Orphans TV series premieres on Tuesday 6th March on Animal Planet across Africa, as well as in Holland, Belgium, Finland, Norway, Denmark, Sweden, Greece, Croatia, Hungary, Turkey, many other European countries, across the Middle East and Russia. I’m currently seeing how I can get you a copy of Groen so you can see the exposure you got. I might have to wait until all 13 episodes of WAO is aired before sending to you, hope that’s ok.

 

With best wishes,

 

Lucy Hale

Fundraising and Marketing Manager

N/a’an ku se Foundation

www.naankuse.como the whole team at Sirtrack,

I wanted to personally send you our 2011 Thank you video which highlights the achievements we have made together for the people and animals at N/a’an ku sê. Thank you for everything you’ve done in 2011 to help make this happen – from sponsoring collars to help us safely release threatened cheetahs and sharing our news and stories with your clients - here’s to a successful 2012 together!

Please enjoy it and feel proud of the difference you’ve made:

http://www.youtube.com/watch?v=k-wHpBVytrI&feature=plcp&context=C300d1dbUDOEgsToPDskK2BT7ILrG91-MWctn4Pyx9

Just to let you know, our Wild Animal Orphans TV series premieres on Tuesday 6th March on Animal Planet across Africa, as well as in Holland, Belgium, Finland, Norway, Denmark, Sweden, Greece, Croatia, Hungary, Turkey, many other European countries, across the Middle East and Russia. I’m currently seeing how I can get you a copy of Groen so you can see the exposure you got. I might have to wait until all 13 episodes of WAO is aired before sending to you, hope that’s ok.

 

With best wishes,

 

Lucy Hale

Fundraising and Marketing Manager

N/a’an ku se Foundation

www.naankuse.com