Surveying Greywing and Orange River Partridges

25 Jul 2009 - by Dr Aldo Berruti

Introduction

How many gamebirds – this is the basis of any sustainable shooting. Amongst the most difficult birds to census are the partridges and francolins. Viljoen (2005) advocates one of two techniques for partridges strip counts, road counts and call counts. My understanding of the professional hunters offering Greywing and in preparation for field trials, the organisers will spend a great deal of time searching with dogs to ascertain the location of coveys.

Total versus comparative counts

One needs to be clear as to whether one wishes a total census of birds (a count of the entire population) or an index count which is used for comparison from year-to-year or area-to-area. With a total count, one can then calculate a percentage off take for an absolute number of birds to be harvested. A comparative count in an area, and then use this index against birds harvested over a period of years to gain an understanding of what are acceptable harvest limits.

Census of Partridges

Viljoen (2005) advocates the use of trained gundogs as the best way to census most partridges and francolins, but also notes that the drawbacks are the amount of time required and the possibility of double-counting. He proposes the use of dog counts supported by road counts. Road counts and dog counts in the same area will produce an index (more birds are seen using dogs) and then these ratios are used to determine bird densities in area classed as high, medium and low-density for gamebird species in question. Cleary, definitions of whether an area if a high, medium or low density is based on experience and is can be subjective.

Census of partridges at Fairview Farm, Vrede

This article reports on the techniques which we have used at Vrede for surveying Greywing and Orange River Partridges, and which are a combination of road visual counts, dog counts and call counts. It produces an effective total count for a farm of 4 000 ha.

Census takes place in May and June after the coveys have formed. If census is undertaken before coveys ar eformed, one obtaisn a very confused picture of covey distribution and the mean covey size is rduced. We use a combination of call counts at dawn combined with the use of a dog to ascertain covey size. The process depends on a pre-dawn departure to be in place as the sun comes up. The peak calling period for coveys is before dawn to about half-hour after dawn. Calling continue aftr this and ther is also a smaller peak in clling near sundown (Little & Crowe 1992). Frequently, I have watched a calling bird respond to the call from a distant covey, and in a high-density area, one can hear as many as four or five coveys from one point. A map of the Fairview Farm and surrounding areas is used to mark the site of calling coveys. Where a covey occurs close the road, a trained gundog (Bella) was used to locate, point and then flush the covey. Experience has shown that estimates of covey size based on visuals often miss one to several birds which are slightly separated from the main group by a few metres and which are sitting tight. This technique is very useful in area of high density, and one can establish the relative positions of several coveys within a short period of time. After stopping at one point, one would then drive for another 300-400m before stopping again.
A vital prerequisite is being able to distinguish between similar calls of the partridges: the calls of Greywing, Redwing and Orange River and Shelley's Partridges are all variations on a theme and familiarity is essential where these species overlap.

Over 2006-2008, the location of coveys has remained constant from year-to-year with little variation, and we know where to expect the coveys. Over the last three years, we have seen covey size increase dramatically and the overall numbers in the survey area

It currently takes 3 days to have census nearly all known coveys using this technique, requiring 2 hours per day. This leaves the balance of the day free for other work, which can include further surveys using dogs for isolated coveys.

Discussion

Why does it work well? At Fairview Farm, Vrede, the roads bisect the high-density areas. In the early morning, the Greywing Partridge are often located next to the road (Berruti and Lowry 2008). A vehicle allows one to traverse greater areas than can be done by walking. It is frequently possible also to get group sizes for as many as 4-5 coveys in a single morning by a combination of visual sightings on open roads or by location and flushing with a gundog.

To search this area on foot with a dog, would require an estimated four field-days with five hours searching per day. This technique requires about 7.5 hours over 5 days in comparison to 20 hours over four days for ground-searches with dogs. It thus leaves the bulk of the day free to undertake other activities. Otherwise, one is faced with the problem that coveys found over a period of several hours during ground counts may be repeat counts.

The technique of vehicle-based counts on roads, combining visual and call counts and dog counts to ascertain covey size will obviously not work if there are no roads. However, the principle remains the same – if one is in position during the peak dawn period of calling, then one can locate the relative positions of several coveys within a short period of time. The shortcoming is that it does not necessary tell one where the birds will be when hunts take place later in the morning or afternoon.

Dr Aldo Berruti

References

Berruti, A and Lowry, N. 2008. The importance of roads to South African partridges and francolins. AGRED Newsletter, June 2008.

Little, R.M. & Crowe, T.M. 1992. Vocal behaviour of Greywing Francolin can be used to estimate population density. Ostrich 63: 98-109.

Viljoen, P.J. 2005: AGRED’s Gamebirds of South Africa - Field Identification and Management. Johannesburg: AGRED.