Breeding seasonality and primary moult parameters of Euplectes species in South Africa

TL;DR: Yellow Bishops have rounder wings than other weaver species, possibly because their larger size affects flight aerodynamics, and the longer duration of primary moult of the Yellow Bishop may be related to food.

Abstract: The grassland biome in South Africa has a summer rainfall and Southern Red Bishops Euplectes orix , Fan-tailed Widows E. axillaris , White-winged Widow E. albonotatus , Red-collared Widow E. ardens and Long-tailed Widow E. progne breed from October or November to March. Primary moult starts in late March or early April. The widows with long tails (Long-tailed and Red-collared Widows) have moult durations of two months, while the widows with shorter tails (White-winged and Fan-tailed Widows) had moult durations of 1.5–1.7 months. Moult ends in late May or early June. Long-tailed Widows have rounder wings than other weaver species, possibly because their larger size affects flight aerodynamics. In the winter rainfall region, Southern Red Bishops and Yellow Bishops E. capensis start breeding after the winter rains, from August–November, and moult starts in early December. Primary moult duration in Yellow Bishops is relatively long, at 3.4 months. Yellow Bishops grow individual primary feathers at an average rate of 21.3 days per feather, while the other species moult primaries more quickly: White-winged Widow 8.1 days, Fan-tailed Widow 11.3 days, and Red-collared Widow 14.4 days. The number of primaries growing simultaneously is similar in the different species. The longer duration of primary moult of the Yellow Bishop may be related to food. Ostrich 2006, 77(3&4): 142–152

Summary

Introduction

• There are seven breeding species of Euplectes bishops and widows in South Africa (Tarboton 2001) .
• Species in this genus in South Africa have their distributions centred on the grassland and savanna biomes in the eastern parts of the country; Southern Red Bishops Euplectes orix and Yellow Bishops E. capensis extend into the eastern fynbos region of the Western Cape (Harrison et al.
• This paper examines the relationship between the timing of primary moult and the timing of breeding in the annual cycles of six of the seven Euplectes species of South Africa.

Methods

• Breeding seasonality data were obtained from the BirdLife South Africa Nest Record Card Scheme (NRC): Avian Ringing data were collected by ringers in the standard SAFRING (South African Bird Ringing Unit) electronic format.
• The primaries were dried in an oven at 60°C for 24h to eliminate moisture and then weighed (Ohaus GA200D balance, precision 0.0001g).
• Underhill and Joubert (1995) showed that within the Charadriiformes, the relative masses of the primary feathers were so similar that the average value for the species for which data were available could safely be used for species for which data were unavailable.
• Presentation in tables of the statistical results of the Underhill-Zucchini moult model includes the following information: mean starting date, standard deviation of the start date, mean duration of moult, and mean completion date.
• Thus, 95% of birds are estimated to start moult during the period from 1.96 standard deviations below the mean to 1.96 standard deviations above the mean.

Results

• Within South Africa, breeding by Euplectes species began earliest in the Western Cape; the median date of egg laying in this province was September (Table 1 ).
• Moulting birds were captured throughout the moulting season , sometimes in large numbers, enabling moult parameters to be estimated reliably.
• Southern Red Bishops in the Eastern Cape showed a moult duration of 3.0 months, with moult starting in late April (Craig et al. 2001, Table 3 ).
• Numbers of primaries growing simultaneously were similar in the five species: Southern Red Bishop 1.7, Yellow Bishop 2.0, Fan-tailed Widow 2.2, White-winged Widow 1.9, Red-collared Widow 2.3, and Long-tailed Widow 2.2.
• In the six Euplectes species considered, the mean starting date of primary moult was 2.5-4.3 months after the median egg laying date and 0.9-2.3 months after the 95th percentile of egg laying (Table 5 ).

Discussion

• The rounded wing shapes of the Long-tailed Widow, compared to the Southern Red Bishop and White-winged Widow , are probably due to adaptation rather than phylogeny ( males have larger wings than females, to compensate for the aerodynamic costs of a large tail in the male (Balmford et al. 1994) .
• Whether there is a difference in relative primary feather masses between males and females is worth investigation.
• Seeds are probably scarcer in the fynbos habitats of the Yellow Bishop than in the grassveld occupied by the other Euplectes species; it is therefore not unexpected that the duration of moult of the Yellow Bishop is c. 65% longer than the average of the species in summer rainfall areas (Table 3 ).
• It would be beneficial to obtain moult records for the Yellow Bishop from other parts of their range, to understand how the timing and duration of moult is adjusted in different environmental regions.
• The delay between the end of breeding and start of primary moult varied from 0.9-1.7 months.

Figures

Figure 2: Capture sites for adult widow birds in South Africa, showing sites from which primary moult data were obtained. Open circles in the Western Cape represent Yellow Bishop records; open circles in KwaZulu-Natal are for Fan-tailed Widow records; open circles in Gauteng are for White-winged Widow and Red-collared Widow records; closed squares are Long-tailed Widow records. Southern Red Bishop ringing sites are not shown (for clarity), but overlap with the ringing sites shown in Gauteng, Kwazulu-Natal and the Western Cape.

Figure 1: Distributions, in southern Africa, of five Euplectes species that occur in South Africa. Darker shading indicates higher reporting rates (from Harrison et al. 1997); the Southern Red Bishop occurs throughout South Africa. The figure at the bottom right-hand side of the page shows the grassland biome (from Allan et al. 1997)

Table 4: Estimates of the primary moult parameters of individual primary feathers for adult widow birds in South Africa

Figure 4: Timing of egg laying and primary moult for adult Euplectes species in different parts of South Africa. The open circles on the thin solid line show the proportion of eggs laid per month (from the Nest Record Cards summary by Prŷs-Jones and Newton 1987); the solid diamonds represent PFMG (Percentage Feather Mass Grown) values by date; the solid diagonal line joins the estimated mean start and end dates of moult; the diagonal dotted lines show the approximate 95% confidence intervals of moult scores on any given date. (a) Southern Red Bishop, breeding and moult records in the Western Cape; (b) Timing of breeding and primary moult in Yellow Bishops, Western Cape (grids 3318–3418), using eather masses of White-winged Widow;; (c) Timing of breeding and primary moult in Fan-tailed Widows, grid 2930 (KwaZulu-Natal), using feather masses of White-winged Widow; (d) Timing of breeding and primary moult in Whitewinged Widows, Gauteng (grids 2527, 2528, 2627, 2628)

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Breeding seasonality and primary moult parameters of euplectes species in south africa" ?

In a recent study, Ostrich et al. this paper found that the primary moult duration of the Southern Red and Yellow Bishops is relatively long, at 3.4 months. 

Q2. How long does the yellow bishop take to grow?

Adult Yellow Bishops needed 2–4 weeks to grow individual primaries, while the other species moulted individual primaries more quickly. 

Q3. How long does the white bishop take to moult?

They estimated duration of moult to be 110 days in Southern Red Bishops, 100 days in male Fan-tailed Widows, and 80 days for Red-collared Widows and female Fan-tailed Widows. 

Q4. What is the average length of the tail of a male and female?

The mean tail lengths of male and female Long-tailed Widows are 411mm and 62mm, respectively (Hockey et al. 2005);males have larger wings than females, to compensate for the aerodynamic costs of a large tail in the male (Balmford et al. 1994). 

Q5. What was the type of data used to estimate the parameters of primary moult?

The data were considered to be of ‘Type 2’ of Underhill and Zucchini (1988), because full moult scores were recorded for each bird and all birds were considered to be available for sampling throughout the moult period. 

Q6. What is the average number of records for the underhill-zucchini moult?

For Long-tailed Widows, 279 moult records were available (166 records for Mpumulanga, 55 for the Free State, 53 for Gauteng, and five records from other provinces).