4.5. Potential role of agricultural intensification in the
decline of Ortolan Bunting
Our results show the importance
of specific habitat characteristics such as high crop type diversity and
availability of bare ground for the Ortolan Buntings. These preferred
habitat characteristics are more typical for traditional, small-scale
farming. The results also highlight regional variations. Notably,
regions with higher agricultural intensification, like South-West
Finland, showed lower population growth rates, suggesting a potential
link between intensification and population decline. The fields occupied
by Ortolan Buntings in North Ostrobothnia are usually rather new fields
and have thus not been under intensive agricultural management as long
as the fields occupied by Ortolan Buntings in South-West Finland have.
Agricultural intensification may have detrimental effects on
biodiversity through several means. Concerning the Ortolan Bunting,
reductions in prey availability or accessibility due to habitat
deterioration on the breeding grounds could be one of the main reasons
behind the negative population growth rate of the species. Also, the
role of nest predators might have changed due to habitat deterioration
caused by agricultural intensification. Habitat change might have forced
birds to nest in unsafe habitat types or reduced availability of
alternative food sources may have caused generalist predators to change
their diets (Evans, 2004). Krüger et al. (2018) showed that the Raccoon
Dog (Nyctereutes procyonoides ) is a potential new mammalian nest
predator successfully invading agricultural habitats in Finland. The
Raccoon Dog has colonized the country within the past 70 years, starting
from the Southeast Finland and now has a distribution which covers most
of Finland, except the northernmost parts (Kauhala and Kowalczyk, 2011).
However, the densities of Raccoon Dogs are not yet high in the North
Ostrobothnia region (Natural Resources Institute Finland, 2022), which
could partly explain the higher growth rates of Ortolan Bunting there.
Another, potentially also very damaging, predator is the feral cat which
probably has an equal effect in all regions. The impact of increasing
effectiveness of plant protectants (pesticides, herbicides, insecticides
etc.) on the breeding and survival of Ortolan Buntings also remains
unknown. Eng et al. (2019) studied the effect of neonicotinoids on
migrating White-crowned Sparrows. They found that ingestion of
imidacloprid by the birds during migratory stopover caused a rapid
reduction in food consumption, mass and fat, and delayed their
departure.
In summary, although our study did not directly investigate the
relationship between the level of intensity of agricultural practices
and the population growth rate of Ortolan Bunting, our results, however,
suggest a potential adverse impact of agricultural intensification on
the decline of this species.
5. CONCLUSIONS AND
CONSERVATION IMPLICATIONS
Current conservation efforts in farmland areas seem to be ineffective in
mitigating the negative effects of agricultural intensification on bird
populations. Measures taken so far might simply be too light to
influence declining farmland birds. At present, it is often unclear
whether current conservation measures have beneficial impacts at all or
whether the measures are just inadequate, either at the local scale (too
narrow field margins for example) or at the wider scale in which they
are applied (too few farms applying the measures).
To conserve the Ortolan Bunting there clearly is a simultaneous need to
avoid abandonment of agricultural areas, and to promote
“de-intensification” of agricultural practices. This general
recommendation would benefit also many other threatened farmland
species. However, in the case of this very rapidly declining species, it
is evident that more precise and finely targeted conservation actions
need to be taken urgently at the remaining and still (somewhat) viable
singing group locations.
Based on our results, we recommend applying conservation measures which
increase the diversity of crop types. Often a field with a greater
diversity of crop plant types also includes more bare ground as a result
of various plant structures and related managing practices.
Alternatively, if increasing diversity is not feasible, or additionally,
we recommend establishing non-crop growing stripes of ploughed bare
ground. We also recommend targeting these actions to populations living
in interconnected farmland landscapes and in northern parts of the
species’ distribution range as it is more likely that these populations
act as sources, rather than sinks, of population growth.
In general, we agree with several researchers stating that we need more
multi-functional, mixed, agro-ecologically managed agricultural
landscapes that promote agricultural yield, biodiversity, and ecosystem
services to conserve biodiversity in farmlands (Baudron et al., 2019;
Tscharntke et al., 2012; Wilson et al., 1997).