Small game and other ground-nesting animals are struggling with climate change and agricultural change. dr Daniel Hoffmann writes about the partridge, its preference for open landscapes and current situation. And about what animals and climate change have to do with each other. Soil is used differently, climate change is causing problems for species.
Information on the partridge - what do animals and climate change have to do with each other?
The partridge is described in the literature as the original bird of the steppe and was only able to expand its range to Central Europe thanks to people working in agriculture. The partridge is well adapted to these original open-land habitats thanks to its compact physique and its camouflage-colored, grey-brown plumage patterned with longitudinal stripes.
As a drought and warmth-loving species, water-draining, mostly sandy soils are preferred, while water-logging and cold gleye and moor soils are largely avoided. Its modern range extends from Great Britain across Central Europe to the Asian steppe regions. The northern border is in southern Scandinavia. In this respect, one would like to think that animals and climate change have little in common.
What the partridge eats
The food of the partridge is mostly vegetable (seeds, green parts of plants). Preferred food plants are field weeds as well as seeds and the fresh tops of cereals. However, the newly hatched young birds are dependent on insect food for their survival. Ants and their pupae are very important, with the lack of above-ground anthills, which are largely absent due to intensive cultivation, making access to food more difficult. Only from the fourth week of life does the proportion of animals fall below 50 percent (Bezzel 1985).
A total of eight subspecies are described based on different plumage colors, whereby the phenotypic variations do not necessarily mean differentiation into subspecies.
The habitat of territorial resident birds such as pheasant and partridge
The partridge is a resident bird in Central Europe. As early as late winter (February–March), the pairs occupy the breeding grounds, which the partridges mark with distinctive “kierr-ik” calls. The nest is well hidden on the ground. A certain variability of the nest construction can be seen, but the partridge has very specific demands on the landscape. Hedges with overhanging grass and strips of old grass along fences are assumed, while fallow land, wild fields, edges of field wood islands and ruderal corridors are the main nest sites in largely hedgeless agricultural landscapes. Base areas of high-voltage pylons are also used, with a very high percentage of open grain fields being selected from France and Poland.
Laying usually begins at the end of April/beginning of May (e.g. average laying start in Baden-Württemberg May 10; cf. Hölzinger 2001). The clutch consists of 10-20 eggs and is incubated by the female for 23-26 days while the male stands guard nearby. Typical for bottom nesters with escaping young, incubation only begins after the last egg has been laid, so that the chicks hatch in June. The young are led by both parents. The partridge only broods once a year, however, early clutch losses result in subsequent clutches, which usually have significantly lower egg numbers. After the breeding season, the families remain together in so-called “chains” for a long time.
Dangers to the partridge
When the chains break up from February, individuals or pairs that are unable to find a suitable breeding area near their winter habitat migrate away. As a result, strong population changes can be observed in the winter habitats within a few weeks. The losses during this dispersion phase can mean death for 50 to 80 percent of the individuals. In unfamiliar territories, which in current landscape conditions are mostly very monotonous, partridges easily become prey of various predators. According to radiotelemetric studies, the goshawk can be considered the main predator at the edge of the forest and at the beginning of the growing season with low levels of vegetation (Petry & Hoffmann 2008). In the later course of the year and thus higher vegetation, foxes and martens come to the fore as the main predators, since visibility, which is crucial for the hunting success of birds of prey, for example, is more difficult. The land predators use their keen sense of smell to find their way around, which is why young birds and breeding females in particular tend to be preyed more frequently.
The evolution of partridge habitats
With favorable habitat equipment, partridges require a relatively small year-round radius of action (usually < 100 ha). According to telemetry studies, the territory size during the breeding and rearing period is less than 2 to about 5 hectares. A varied field with distinctive dividing lines such as crop rotations, old grass strips, wild fields, ditches or hedges is decisive for a high density of breeding pairs, as otherwise neighboring cocks often fight and the territories are significantly enlarged as a result. Older studies have shown settlement densities of more than 50 breeding pairs per 100 hectares of open land, while today local densities of five territories per 100 hectares of open land are considered high and are only found in exceptional cases. Due to the negative population development in large parts of its Central European breeding area, there are currently only densities of well under one territory per 100 ha of open land in many areas and parts of the original breeding area are already deserted or will no longer house any partridges in the foreseeable future.
Compared to the 1960s and 1970s, the hunting distances of the partridge have fallen to less than five percent, in some cases to less than one percent, depending on the federal state. However, the development of the hunting range does not allow us to draw conclusions about an actual population development, since the data over longer periods of time are not comparable due to the voluntary waiver of hunting practiced by hunters for decades. However, based on atlas maps and more or less representative studies, it can be assumed that the number of partridges in Germany has declined by around 70 to 80 percent over the last 25 years. This makes the partridge, along with a few other ground-nesting species, the frontrunner in terms of population decline. Animals and climate change have something to do with each other here.
Photo: Unsplash/Taylor Siebert
The Geography of Pheasant and Partridge
In principle, the partridge is relatively easy to map, and the estimates based on observations and interrogations by hunters also produce useful results according to the current state of knowledge. However, not every method can be used to obtain relevant population data. Mapping for breeding bird atlases has turned out to be of little significance for the partridge, since atlas mapping is primarily designed to record the common bird species. Special studies to record inconspicuous species or species that are difficult to record, for example with sound dummies, cannot be a comprehensive part of these large mapping projects. In the breeding bird atlas of Schleswig-Holstein (Berndt et al. 2002), for example, a state population of around 1,900 breeding pairs of partridges is given, while mapping by the WildTierKataster Schleswig-Holstein (Landjägerverband Schleswig-Holstein) extrapolated almost 8,000 pairs. In order to clarify these discrepancies, a study comparing methods was carried out in 2003, after which a population of around 7,000 to 9,000 pairs was stated (Jeromin et al. 2004).
The situation in Lower Saxony
In Lower Saxony, too, the meaningfulness of the mapping by hunters from the local wildlife survey (WTE – Landesjägerschaft Niedersachsen) was checked using ornithological field methods (Voigt et al. 2000). Here, too, it was found in summary that the mapping of the hunters provided very precise information in the case of low and medium stock numbers and only tended to underestimate the stocks in the case of high population densities. The wild animal monitoring, as it has been carried out nationwide in the project Wild animal information system of the federal states of Germany (WILD, http://www.jagdverband.de/content/wild-monitoring) since 2002 or 2003, thus provides reliable figures on the stock and for almost all federal states through regular repetitions of the work on the development of the partridge. No other monitoring is able to derive comparable data over a large area.
The development of animals
The development of the partridge in Germany already shows a significant slump in the early 1980s, which can usually be gathered from hunting reports and reliable oral reports. With the beginning of the first nationwide population estimates in some federal states at the beginning of the 1990s and later in the nationwide WILD, a relatively constant but low level population trend was documented, which only changed significantly again after 2007. With the abolition of mandatory set-aside in 2007, the agricultural landscape changed significantly due to massively intensified maize cultivation in many regions of Germany and a decline in set-aside and fallow land to insignificance in terms of area. Old grassland scars were increasingly turned over, and if they were not converted into arable land, they were converted into intensive grassland with an increased mowing frequency. The remaining habitats of the partridge and many other field species were destroyed and have not been restored to this day. In Baden-Württemberg, a total of 2,703 pairs of partridges were confirmed by hunters in a good 3,700 districts in 2002 (Pegel 2002). In 2011, more than 4,000 districts took part, but only 1,523 pairs of partridges could be confirmed. In a comparison of the survey years 2006 and 2011, slight to sometimes severe declines in the species were reported from all participating districts (cf. WILD 2011).
Animals and climate change in the cadastre
Based on the data from the Northern Statistics Office on land use and the partridge maps from the WildTierKataster project (www.wtk-sh.de), statistically significant evidence could be provided that through intensified maize cultivation, particularly in the old moraine landscapes of the Hohe Geest and Vorgeest, where the soil quality is rather low, where however, the best gray partridge habitats were previously proven, the overall most significant population declines are recorded (Schmüser & Hoffmann, unpublished). Maize cultivation in Schleswig-Holstein increased from around 80,000 hectares to over 180,000 hectares between 2002 and 2010 (Statistics Office North 2002 to 2010).
Bavaria is different
Counts or estimates of the number of partridge breeding pairs are therefore available from most federal states with the exception of Bavaria, where a record is only available for the years 2002 to 2006. For Saarland, there are surveys from WILD for the years 2002 to 2013, and a state-wide survey using a comparable method was carried out as early as 1991 (Guthörl 1991).
Based on the time series and in connection with data on land use as well as climatic conditions and information on red fox densities, the reasons for the considerable decline in the gray partridge over the past almost 25 years can be discussed (cf. also Hoffmann & Hoffmann 2015). The work of the wildlife information system in Saarland is being intensively supported by the Saarland Hunters' Association.
Predation affects animals
With regard to land use in Saarland (Stat. LA 1991 to 2013), it is understandable that land use in Saarland remained relatively stable in the years 1991 to 2002. The fallow areas are hardly subject to any changes during this period. The share of winter oilseed rape is only slightly increasing. During this period, however, there is already a noticeable decline in spring barley, which among the cereal types still had a relatively high proportion of area with significant annual fluctuations until the late 1990s. In the period between 1991 and 2002, a loss of more than 40 percent in the partridge population can be observed with relatively small changes in terms of area.
Many enemies
During this phase, the population densities of the red fox increased significantly, in particular due to the nationwide rabies immunization. If the hunting distance is used as a relative measure of the abundance, at least a threefold increase can be assumed. Furthermore, after the ban on hunting in 1987, the numbers of carrion crows increased significantly. According to these results, the declines in the 1990s are likely to be due in particular to increased predation rates, while agricultural use cannot be presented as insignificant, but must be shown as a secondary factor. Animals and climate change are thus related in that changing conditions lead to an increase in predator populations. As already discussed by Potts (1986), the gradual switch from spring crops with winter stubble to the higher-yielding winter crop varieties can be considered as part of the cause of the decline.
It's the mix that counts! Small game love varied field structures and crop rotations. This also includes vineyards and fallow land. Photo: Unsplash/Markus Winkler
The soil as a decisive factor
In the following decade of the 2000s, a stabilizing predator population at a high level can be assumed. The partridge continues to lose population size and by 2009 has reached a new low of only around 0.5 breeding pairs per 100 hectares of agricultural land. The area under spring barley has fallen to just 25 percent compared to the 1990s and is on a linear downward trend. At the same time, grass cultivation on arable land is gaining in importance and the gradual conversion from grazing to mowing for silage production is also progressing in a linear trend. After 2007, the landscape change intensified and fallow land fell by more than 50 percent from a good 4,000 hectares to less than 2,000 hectares (Stat. LA 2002 to 2009). The partridge losses between 2002 and 2010 can be attributed to the changes in agriculture to a highly significant extent. Increased cultivation of maize and winter oilseed rape, grass cultivation on arable land and changes in use of permanent grassland have a statistically significant negative impact on partridge populations. Land uses with significantly positive influences on the partridge population, such as fallow land and summer grain, as well as limited pastoralism, are gradually being pushed out.
Animals and climate change - It's all in the mix
After 2010, two further investigation years of the wildlife information system can follow with 2011 and 2013. After a certain stabilization at a low level between 2005 and 2010, there is a renewed decline of another 50 percent. From 2011, according to the surveys, approx. 0.25 pairs per 100 hectares of agricultural land can still be expected. Fallow land and spring barley continue to decline, although the sharpest falls in these two types of use have already occurred in the previous decade. With the exception of maize cultivation, which is gradually gaining in importance, the other land uses discussed in the previous chapters remain largely stable. After 2009, however, hunting of the red fox in Saarland changed. A half-year closed season for foxes between 16.02. and the 15.08. has probably contributed to the fact that the frequency of prey-seeking foxes and young foxes has increased during the partridge rearing period. Limited habitat availability for the partridge due to changed habitat qualities, especially after 2007, may have increased the influence of predators.
Necessary measures for the partridge
In order to ensure the survival of the partridge in Saarland and ultimately in the entire south and south-west of Germany, timely measures are required. The so-called "greening" as an attempt to ecologize agriculture can be a building block if, as far as possible, flower and fallow strips with year-round cover, rest and food are established in the landscape in a mosaic-like manner. In addition, the targeted promotion of summer grain with winter stubble should be included in the program for the following funding periods of the EU's joint task for agricultural policy (GAP). This means that a certain productivity can be maintained on the land, and at the same time the summer grain combined with winter stubble offers good basic conditions for many farmland birds and demonstrably for the partridge. The hunting of generalistic predators should experience an intensification. If this cannot be achieved by the hunters across the board, then fox and carrion crow hunting must be intensified at least in the field areas with potential partridge occurrences. Some benefit, others don't. Animals and climate change are related. The legal options for this should be significantly expanded in Saarland, as in other federal states, rather than reduced. It is becoming increasingly unlikely that the gray partridge will be able to survive in the cultivated landscape without countermeasures. Based on the Saarland evaluations, two Saarland districts can already be described as "roe chicken-free" according to the recording results from 2013 (Hoffmann & Hoffmann 2015.).
What is the impact of climate change?
The conversion of an agricultural cultural landscape into almost fallow-free production sites for agricultural and energy products has reached its peak in the recent past from 2007, with the result that the landscape capacities for types of open land have been significantly reduced. Breeding locations, seeds of wild herbs, cover and insects have been pushed back to such an extent that successful breeding and rearing are hardly possible. Added to this is the high presence of generalist predators, which in some regions is intensified by the spread of neozoa. Developments in the gray partridge and some large-scale analyzes suggest that the species was dependent on set-aside and fallow at its 1990s and 2000s population levels.
Animals and climate change - Soil is not just soil
Due to changed agricultural subsidy regulations, these habitats have essentially been lost, so that the landscape capacity has further decreased, resulting in a reduced stock level. The influence of predators is further intensified in the remaining habitats, as they specifically search for potential breeding and rearing areas.
Attempts are currently being made to reverse or restore the conditions before 2007 by means of so-called “greening”, but this cannot be successful if large areas are only “greened” in winter. Although this means that individual individuals are more likely to survive the winter, there is still a lack of breeding and rearing habitats. Likewise, the increased surface area of intensively and frequently mown grassland is meaningless from a floristic and faunistic point of view.
Animals and climate change - what influence biotopes have
If the management guidelines for a real area of at least 5 percent of the agriculturally used area do not change within a short period of time in such a way that year-round biotopes are created in the landscape like a mosaic, the partridge will become extinct along with other species in the region. However, species protection can only be successful in cooperation with landowners and managers, because society as a whole bears responsibility for biodiversity. Appropriate compensation for the provision of land, its cultivation and to compensate for loss of income must be paid in an economically relevant amount.
Conclusion – The partridge as a key figure in climate change?
While society is dealing with the unapproachable issue of global warming, biodiversity is being lost in Central Europe without taking climatic changes into account. Doing one should not mean neglecting the other, especially in rich nations. CO2 reduction as a buzzword is only part of our responsibility. How should species protection as a task for humanity be credibly communicated in poor regions that are considered hotspots of biodiversity on earth, when the comparatively few species in Europe are deprived of any basis for life through state support, political ideologies and one-sided subsidy practices?
Animals and climate change - without hunting, it doesn't work!
The question then arises as to who has made a valuable contribution to the preservation and also the basic monitoring of the species? Without the initiatives of the hunting associations and the broad participation of the hunters on site in wildlife information systems and voluntary, honorary nature conservation measures with a simultaneous voluntary waiver of hunting, knowledge of the population development of the species would be marginal on the one hand and the few locally still good stocks without hunting would be even rarer. Politically it sends the wrong signal if, as in Baden-Württemberg, the responsibility for the preservation of the partridge through the classification into the so-called "protection management" is only pro forma the responsibility of those authorized to hunt. Because animals and climate change need hunting. Such a policy offers no prospects for the future and this will always be at the expense of the partridge. It will be in vain to look for interest groups that take on hunters instead of the species with comparably persistent commitment. Most recently, the government of the Grand Duchy of Luxembourg has completely banned fox hunting. This is primarily to be interpreted as total opposition to hunting and species protection, which makes it clear that some politicians are pushing through their own ideologies, disregarding all scientific knowledge and practical examples.
