Restoring the red-listed grey partridge across the North Sea region: Lessons from the PARTRIDGE project

12 September 2023 - Published by Francis Buner
Against the backdrop of the concerning decline in farmland species across Europe, our project set out to demonstrate how targeted management measures can restore farmland biodiversity by up to 30%. Central to our efforts was the grey partridge, chosen as the flagship species of our project for its dual role as an umbrella species for farmland biodiversity and a key indicator of overall farmland ecosystem health. Where partridges thrive, biodiversity is high and ecosystem services are intact. Over the course of the seven project years, we focused on establishing wildlife-friendly habitat on at least 7% of 10 demonstration sites spread across Belgium, The Netherlands, Germany, England, and Scotland. This wildlife-friendly habitat, coupled with supplementary winter feeding and predator management where feasible, aimed to create a more hospitable environment for these ground-nesting farmland inhabitants and, ultimately, promote overall farmland biodiversity.

To assess the effectiveness of these measures, we closely monitored local partridge populations at the 10 demonstration sites and 10 paired reference sites (where no additional measures were implemented). However, the elusive and well-camouflaged nature of these farmland residents makes them masters at hiding in plain sight. To overcome this, we employed the line-transect playback method, using the call of a male partridge to provoke responses and make them more visible during counts.




GWCT placement students getting ready for a grey partridge line transect spring count at the Rotherfield demonstration area


This method was originally developed and tested by our German partners from the University of Göttingen with slight adjustments made for our transnational project. Throughout the project's duration, countless sunrises and sunsets were spent covering the extensive network of line-transects scattered across our project sites, eagerly awaiting the all-too-familiar 'kieer-iek' response from reactive males in the field. If you're curious to know more about these exhilarating field experiences or the method we employed, we encourage you to check out our factsheet, monitoring blog and video.

After seven years of meticulous monitoring, the data revealed that, on average, twice as many partridges were present at the demonstration sites compared to the reference sites (Figure 1)!

This finding was further supported by our breeding bird monitoring (also part of our project’s monitoring programme), where we found that, on average, our demonstration sites hosted 70% more breeding territories for grey partridges compared to the reference sites. These results underscore the positive influence of improved habitat quality on local partridge populations. The measures implemented at our demonstration sites, aimed at providing secure nesting and brood-rearing habitat with ample food during winter and protection from predators and harsh weather, fostered an optimal environment for these valued farmland residents.



Figure 1. Number of counted male partridges per kilometer in demonstration and reference sites per site (grey) and for all sites combined (colour) (2021-2023). Error bars represent confidence intervals. Naming based on the abbreviated country name followed by the demonstration site name.


However, as discussed in our brown hare monitoring blog, habitat mapping revealed that most demonstration sites were already in good condition at the project's outset, with some even surpassing the targeted 7% beneficial habitat coverage in 2017. To isolate the effects of our additional measures from the impact of pre-existing habitat quality, we compared the trends in partridge numbers between demonstration and reference sites. Ideally, partridge numbers should have increased more rapidly at the demonstration sites compared to the reference sites. Yet, much like the brown hare monitoring results, this trend comparison showed that the overall partridge number trend did not significantly differ between the two types of sites, with outcomes varying substantially among our project sites (Figure 2). This could suggest that, although our measures were undoubtedly valuable, they might not have had enough impact on the population trend to be detectable with our monitoring efforts.



Figure 2 Difference in partridge spring monitoring trend (%) between demonstration and reference sites per site-couple (green) and overall (blue). Point estimate and 95% interval. 0%: no difference; 30%: project’s target. Differences are considered significant when the 95% interval does not include the 0% reference and non-significant if it does. Naming based on the abbreviated country name followed by the first four letters of the demonstration site name.


Furthermore, trend analyses are notoriously difficult, often requiring extensive sampling efforts and time to distinguish between natural year-to-year population fluctuations and the effect of our implemented management on the overall trend. This is especially important for species at low population densities, such as the partridges on our project sites.



Volunteers handing back field protocols after a successful count


While the seven years of monitoring at our 500-ha demonstration sites yielded valuable insights; an even longer monitoring period and larger study areas might be necessary to accurately assess the full impact of our measures on partridge population trends. Additionally, factors beyond habitat quality, such as predation, disease, dispersal, human-induced fatalities (e.g. mowing, ploughing, road traffic accidents), and methodological artefacts, may have equally influenced the fluctuations in partridge numbers at our project sites, making it even more challenging to pinpoint the precise impact of our measures on local partridge populations.

In conclusion, our monitoring results provide compelling evidence for the vital role of targeted management measures in restoring local partridge populations and overall farmland biodiversity.

The flourishing partridge populations in the enriched habitats of our demonstration sites underscore the importance of habitat quality in supporting farmland wildlife. Nevertheless, the challenges posed by trend analysis, the limits to the length of projects, and the influence of external factors highlight the intricate nature of local partridge dynamics and the complexities involved in evaluating the relationship between management measures and biodiversity.



A partridge male attracted by the playback call used for monitoring


Overall, our results emphasize the ongoing challenges of restoring farmland biodiversity and underscore the importance of considering the long-term perspective in conservation efforts.


 Written by Fleur Petersen, Instituut voor Natuur- en Bosonderzoek (INBO), edited by Dr Francis Buner & Dr Julie Ewald, Game & Wildlife Conservation Trust.