THE ENIGMA OF THE ORTOLAN BUNTING

Based on 895 literary sources published in about 20 European countries during the last 400 years, this book exposes the unreliability of contemporary, model-created hypotheses used as tools to unravel the spatiotemporal development in bird populations, compared to the reliability of historical, empirical material, exemplified by the Ortolan bunting Emberiza hortulana.

The author compared factual historical information about the development and status of the population to current theories, which are based on recently collected data from contemporary research.

Large knowledge gaps were discovered in the understanding of the development and dynamics in the population across the distribution range.

The review also debunked myths now used by researchers as verified scientific data to support current views on ortolan bunting ecology and population trends.

In addition, the historical literature showed that scientific projects recently run in Europe to reveal aspects of the Ortolan bunting's ecology, produced results already known from data collected from 90 to 190 years ago.

This exercise is an example of the advantage of extracting historical, empirical hard data on bird species in general, to better understand spatiotemporal population dynamics not possible to discern by short term tests in current environments.

Current theory posits that the Ortolan bunting is declining  due to human influence through fragmentation of habitat and illegal hunting, especially in France. The fragmentation results in a scattered and "island"-like distribution in Western Europe.

However, the Ortolan bunting is distinctly a valley colonizer and the distribution is due to area selection during colonization, not fragmentation because of population decline.

The bunting breeds on the exact same geographical "islands" today as it has done throughout the last 300 years - and it also does NOT breed in the same areas it did NOT breed in, during the same period.

To superimpose the largest rivers in Europe on a distribution map illustrates the dynamics. 1: Rhine. 2: Main. 3: Ems. 4: Weser. 5: Aller. 6: Elbe. 7: Havel. 8: Spree. 9: Vltava. 10: Elbe (within the Czech Republic). 11: Oder.

White circle: Positive information about absence. Black open circle: Rare. With one crossbar: Common. With two crossbars: Very common.

In the book, 8 maps show the European observation material in time periods from 1724 to 1900.

The Ortolan bunting colonized Western Europe via the river Danube and spread further out through other river valleys in the West- and Central Palearctic Region. 1: Po. 2: Danube. 3: Dniester. 4: Dniepr. 5: Don. 6: Volga-Baltic Waterway. 7: Ural. Currently the center is located in Russia as a result of asymmetric growth from an origin in Western Asia and the large population there serves as a source of immigrants to Western Europe. 

In the 18th-, 19th- and early 20th century 10 different authors all had the impression that the Ortolan bunting colonized Scandinavia from the south and they could not understand the lack of observations between the few which were scattered on the extreme northwestern periphery in Northern Norway.

However, the bunting colonized from the Volga-Baltic Waterway in the southeast, through Finnish Karelia and around the Bay of Bothnia. It then penetrated the mountain barrier between Sweden and Norway through river valleys, and the few breeding areas in Northern Norway were linked via specific valleys to source populations along the Swedish east coast.

This is still the case today, with new observations at the same locations in Northern Norway.

Current scientific literature claims that the bunting avoids coastal areas. This myth arose from the fact that ornithologists in the 1800s claimed that it did not breed in Western Norway, and it was later explained by a 1948 publication stating that the bird has a preferance for areas with less than 600 mm annual precipitation.

The ortolan bunting was found on several locations on the Norwegian west coast from the 1850s to the 1890s. At one of the locations (Førde) it was described as "one of four characteristic species in the valley". On two of the locations, the annual precipitation was 2.755 mm and 2.780 mm. It was also found breeding on grass covered islands in the Guadalquivir marsh Las Marismas in Spain in 1893.

The Swedish naturalist Sven Nilsson undertook two long excursions throughout Norway, in 1816 and 1826. In 1826 he noted "the highest abundance of Ortolan bunting ever recorded in Scandinavia" at location 2 and 4. 75 years later it was still common at the same two locations - as it was on the exact same longitude 85 km due south, at location 6.

Current Norwegian ornithologists are not aware that the ortolan bunting ever bred at these locations, as the population later retracted.

In 1826 this seems to have been the western periphery of the range in South-Central Norway, but from the 1850s to the 1890s the bird bred  as far west as possible, along the coast of Western and Northern Norway north to 67.6 degrees N.

The picture top right shows the habitat at location 2, the picture on the lower right, the habitat at location 6. Both were taken in the early 1900s and show one of the classic habitats for Ortolan bunting - mountain slopes facing south, exposed to intense sunshine resulting in an overpowering heat.

The decline of the ortolan bunting population in Norway has been linked to the biocidal effects from mercury laced seed grain, specifically in conjuction with the "tractorization" of agriculture. Higher speed during sowing led to more spill, and the introduction of "the Little Grey Fergie" tractor with a rear-mounted three-point linkage which could lift the seed drill from the ground (even more spill) has been blamed.

The abandonment of the old grass burning of field and brush has also been suggested as a reason why the bunting declined - as it could have been dependent on such a reduction of succession in the habitat to the lowest possible level (fire burns).

However, the most abundant population Swedish naturalist Sven Nilsson ever recorded in Scandinavia, in 1826, fell to zero in 112 years - and from "common" to zero in  40. This was continuously monitored by 4 ornithologists over a span of 200 years, all but one with doctorates, living at and/or visiting location 2 and 4 in the previous map.

This decline is one of the fastest and most dramatic in Scandinavia, and it happened while grass burning was still common, before the tractor was introduced, i.e. the three point linkage had yet to be invented, sowing and harvesting was done either by hand or horse drawn implements, no mercury laced seed grain was in use and no plausible reason can be found to suspect destructive habitat fragmentation on a region wide scale from human activity.

The perception of a one-way declining trend in the ortolan bunting population in Europe has emerged from data collection over an insufficient period of time.

This population needs to be viewed across centuries and the whole continent - and this may very well be the case also with other bird species. 10-40 years will only give a glimpse into the current trend, but not show the whole picture.

The bunting has always been famous among European ornithologists for radical, unpredictable, inexplicable shifts in distribution and habitat use, with colonizations and subsequent retractions of the periphery  across 60 - 100 years. In the picture on the left a very noticeable colonization and retraction, commented on by multiple ornithologists, took place north to Lorraine between 1760 and 1822.

The picture on the right illustrates movements in the French population throughout the last 260 years, according to information in literature.

The population in Fennoscandia behaves according to the principles in the Abundant Center Hypothesis. There is an exceptionally high immigration rate from the source population in Russia, and it is reason to believe that the variation in this rate over time decides the fluctuations in the trends in Fennoscandia and the rest of Europe, and hence where the periphery runs at any given time.

During the decline in Fennoscandia throughout the last 50 years, the gravitational center in the population has moved increasingly further north in Sweden and around the Bay of Bothnia back into Finland - backwards along the original colonization route from Finnish Karelia.

In 2009, with a Swedish population estimated at 6.300 pairs, 92% was situated north of the 61st parallel, 80% in the three northernmost counties. In 2012 the national estimate had decreased to 3.700 pairs - and the proportion in the three northern counties predictably increased to 87.7%.

A review of the the range boundaries over the last 227 years gives a distinct impression that the eastern part of the range is as broken up as the western - it is just lacking in detailed information.

Since the Ortolan bunting population behaves according to the Abundant Center Theory, the decline in Western Europe since the record abundance in South-Central Norway in 1826 might have been influenced by the deforestation of the Taiga in Siberia. The logging has allowed the Ortolan bunting and other steppe  species to move off of the steppe, onto forest clear cuts and it has effectively pushed the boundary 1.400 km eastwards. This is the same distance as from Eindhoven, the Netherlands, where most of the Dutch population was concentrated about 1950, to Lutsk in Ukraine - i.e. across the entire Western Europe.

The logging has induced asymmetric growth with a subsequent movement of the population center towards the east.

This would have a noticeable effect on the position of the boundary in Western Europe, and hence on the long term population trend.

It has been claimed - and is still claimed both in current scientific literature and on popular sites like Wikipedia - that 80.000 - 200.000 Ortolan buntings were captured in Cyprus every year and exported to Europe as delicacies for the table. This myth was debunked by the German ornithological pioneer Johan Friedrich Naumann already 200 years ago, in 1824. It was reconfirmed as a myth in 1911, and later observations (1968, 2003-2013 and 2021) have also reconfirmed that this is incorrect. All small birds caught for the table were labeled "ortolans" and the author found 34 species and subspecies which had been assigned this name.

The French ornithologist Toussenel described how he was met by the bird catchers of Marseilles in 1859, when claiming that they mislabeled the different species and pointing out that they had buntings and gold finches for sale:

"They may be buntings and gold finches in Paris, but here in Marseilles, they are ortolans".

A summary of accounts of bird catches from Italy, Germany and France from 1611 to the 1880s (275 years) showed that of 409.500 birds taken during 51 seasons, only about 600 were ortolan buntings - 0.15%.

An estimate of average, annual catch between Recanati and Falconara on the northeast coast of Italy in the 1880s, made by "the best experts among the bird catchers" upon request from Italian ornithologists. The proportion of Ortolan bunting among 173.200 birds was 0.17%.