Weaver news

Weaver Wednesday 3 [252] - Range changes [15]: Thick-billed Weaver

2017-04-12 (776)

gravit8 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
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).