Why is the population in decline?

Why are they Disappearing?

Since the 1970s, the population of the Netherlands’ only migrating dove has plummeted by more than 85% in West Europe – the Netherlands itself has seen an estimated 97% decline since the 1980s. It is now a Red List species, with an estimated 1,200 – 1,400 pairs remaining (Sovon, 2018).

The population decline of this dove is a complex and international issue. The main threats are:

Habitat loss across breeding range
Habitat loss across wintering range
Illegal Trapping and killing
Unsustainable hunting
Disease

Habitat Loss in Breeding Areas

Turtle doves require dense scrub or hedge for nesting and roosting, and feed exclusively on seeds. Recent changes in agriculture and land management have reduced the availability of cereals, wildflower seeds and herb-rich hay meadows. In the Netherlands, as in the rest of western Europe, farming has intensified considerably, resulting in greater use of herbicides and pesticides and much larger fields.

The result is an increasing scarcity of the small-scale landscape that breeding Turtle Doves need. This is reducing not only the total number of breeding birds, but also the breeding success of the species; a British study revealed that the survival rate of chicks has more than halved since the 1970s.

To illustrate this landscape change, Figure 1 shows a square kilometre from the Zak van Zuid-Beveland. The landscape changes over the last 50 years are clearly marked by increased field size and a reduction in field edges and hedgerows.

Figure 1: Arial photos from 1970 and 2017 showing a square kilometre of land close to ‘s-Heer Abtskerke

Legal and Illegal Hunting

Turtle doves face massive persecution through legal and illegal hunting. Due to the low survival and low productivity of the species, hunting of any sort is likely to have a severe impact. Unfortunately, illegal hunting figures can only be estimated and hunting figures for many countries are unknown. However, in the EU alone, where the population is estimated at 2.2 and 4.1 million breeding pairs, between 1.3 and 2 million Turtle doves are legally hunted each year**.

Disease

There is also a new and growing concern that the pathogen Trichomonas gallinae could be impacting the Turtle dove population. Although little is known about the disease, it's main carriers globally are Columbidae (doves and pigeons).

Changes in Overwintering Habitat

Turtle Doves spend their winters in the African Sahel - 4000km south of the Netherlands. In order to cross the Mediterranean Sea and Sahara, the Turtle Doves need sufficient food, water and resting places, to build up fat reserves before departure, and to refuel en route. Sadly, the doves are increasingly encountering drought, human disturbance and a shortage of trees and woodlots for resting in. In addition, hunting in overwintering areas also has an effect: if not in terms of direct casualties, then in the disturbance of roosting areas. It would appear that hunting tourism also plays a certain role in this, with travel bureaus even advertising Turtle Dove hunting***.

*Browne and Aebischer (2005) Studies of West Palearctic birds: Turtle Dove. British Birds, 98 (February 2005), 58-72

**Figures taken from the International Species Action Plan for the Turtle Dove, 2018, compiled by Birdlife International, RSPB UK and other partners.

*** Bos, J (2017) Europees beschermingsplan voor de zomertortel: https://www.vogelbescherming.nl/actueel/bericht/europees-beschermingsplan-voor-de-zomertortel