Weaver Wednesday 3: range changes in S Africa
(species text)
Thick-billed Weaver Amblyospiza albifrons
Thick-billed 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).
Thick-billed Weaver, figure from Birdpix
Range changes in SA
Range change summary
More
4 lists
30 lists
increases
n
%
n
%
Decrease
91
22
32
11
Tiny change
71
16
50
18
Increase
270
62
194
71
Total
432
100
276
100
In South Africa the Thick-billed Weaver has many more grid cells with increases in reporting rate than cells showing decreases, between SABAP1 (1987-1991) and SABAP2 (2007-).
The points below match the points on the map above.
Areas with very large increases include:
1. Gauteng and surrounding areas - first reported here in 1961, increased over many decades in urban Gauteng, and in recent years expanding further outwards.
2. Expanding westwards in interior KwaZulu-Natal.
3. Western parts of the Eastern Cape.
Areas with very large decreases:
4. Some decreases along the Mozambique border - this weaver occurs at a lower density here.
Range changes elsewhere
Zimbabwe: increase in Harare, expanding from east (Baker 2011b).
