Weaver news

Weaver Wednesday 3 [240] - Range changes [3]: Sociable Weaver

2017-01-18 (762)

gravit8 Weaver Wednesday 3: range changes in S Africa (species text)

Sociable Weaver Philetairus socius

Sociable Weaver, Range-change map between SABAP1 (1987-1991) and SABAP2 (2007-current).
Red, orange and yellow = cells with very large, large, and small relative decreases
Blue, dark green and light green = cells with very large, large and small relative increases.
Cells = quarter-degree grid cells; Only cells with at least 4 checklists in both SABAP1&2 shown. All cells had this species recorded in SABAP1 or in SABAP2 or in both (more about interpretation at Biodiversity Observations 7.62: 1-13).

Range changes in SA

Sociable Weaver
Sociable Weaver,
figure from Birdpix

Range change summary
More 4 lists 30 lists
decreases n % n %
Decrease 101 37 12 36
Tiny change 74 28 12 36
Increase 97 35 9 27
Total 272 100 33 99
In South Africa the Sociable Weaver has more grid cells with decreases in reporting rate than cells showing increases, between SABAP1 (1987-1991) and SABAP2 (2007-). The points below match the points on the map above.

Areas with very large increases include:
1. the Springbok area,
2. the area north of the Carnarvon to Britstown road,
3. near Barkley West (this is on the southern edge of the Ghaap plateau),
4. and the northernmost part of the Kgalagadi Transfrontier Park.

Large decreases appear to have occurred:
5. along the lower Orange River,
6. in the area from Augrabies Falls National Park to Kakamas,
7. and the area south of Christiana.

8. Absent on the Ghaap plateau:
There is a large gap in range of the Sociable Weaver around the Ghaap plateau, between Danielskuil and Vryburg. The weaver appears to have been absent from here for at least 100 years. There are new records (SABAP2) in the southern part of this gap (point 3), indicating that the Sociable Weaver may be colonising this area northwards.

Range changes elsewhere

Botswana: range extension near Konkwe Pan (Tyler 2008c).