The latest annual combined aerial/ground crane census for the wet season at Etosha National Park and northwards yielded a maximum total of only 13-15 adult Blue Cranes and one young fledgling (all within the park) – a further decrease in adult numbers for the wet season from 32 in April 2010, 24 in April 2011 and 18 in March 2012.
Overall, numbers have declined steadily since the totals of 60 (54 adults and six chicks/fledglings) in April 2006 and 1994 (49 adults and eleven chicks/fledglings), and 80 in 1992. Only four pairs of Blue Cranes were recorded breeding this year, producing at least six chicks although only one (17%) survived to fledging.
On the positive side, the April 2013 census provided a total count of 19 Wattled Cranes, including two within Etosha at Andoni, the first record of this species within the park. This development could be associated with the planned burn that took place at Andoni in July 2012; but climate change may also be playing a factor. The remaining Wattled Cranes were recorded in the Lake Oponono area, together with four Crowned Cranes.
One of the contributing factors to the present low numbers of Blue Cranes could be that the rainfall was lower this year (around 200 mm at Okaukuejo, compared to the long term average of 380 mm) than during the preceding years, and also early. There was very little water in the Pan, while Lake Oponono was also drier.
The cranes breed in the ENP during the summer wet-season months. Once the chicks have been reared and are able to fly, the birds leave the confines of the park and head northwards.
|Fast Facts about the Blue Crane:|
|Height||100 to 200 centimetres tall|
|Wingspan||180 to 200 centimetres|
|Weight||3.2 to 6.2 kilograms|
|Types of Habitat||Grassy Uplands|
|Number of Species of Crane||15|
They have been recorded in the Lake Oponono (Omadhiya Lakes) area at such times, where they feed on “uintjies” (Cyperaceae) found in the well-grazed grasslands.
However, based on the count data, it has become clear that not all the cranes are present in the park during the wet season. During some years they have not been counted at Lake Oponono during either the wet or dry season, and it is not known where they go at such times.
In 2006, due to a concern about the apparent decline in numbers of Blue Cranes, the Namibia Crane Working Group initiated a conservation action plan for the species.
Numbers, breeding success and distribution have been monitored on a regular basis since then. Twenty-four chicks have been fitted with large green plastic rings each with a unique alpa-numerical code and, together with radio telemetry, have been invaluable for tracking movements between Etosha and Lake Oponono, and determining survival rates. Of the breeding birds this year, five (63%) were ringed and aged four to seven years old.
However, additional measures are required to track crane movements on a wider scale. Generous funding has been provided by the Environmental Investment Fund (EIF) of Namibia to fit a Blue Crane with a sophisticated solar leg-mounted GPS satellite transmitter (PTT), and the Namibia Crane Working Group is planning a capture at the first opportunity.
A satellite transmitter has already been fitted a large, just-fledging juvenile east of Salvadora on 7 April 2011, but no further signals were received after 2 May 2011.
Until recently, the fate of the bird was not known as the transmitter had not then been recovered.
On 29 October 2012 the Ministry of Environment and Tourism (MET) collected a (live) Blue Crane fitted with a transmitter about 120km west of Rundu, at Kahenge. According to the number of the bird’s metal ring, this turned out to be the above juvenile. Although the bird did not survive, its discovery on the northern border of Namibia represents a milestone in efforts to map the areas used by the cranes. Blue Cranes have also been reported in Caprivi in September 2007.
All three of Namibia’s crane species are on the red list: the Blue Crane is critically endangered, the Wattled Crane is endangered, and the Crowned Crane is near threatened; all three species are also globally threatened.
* Article supplied by Dr Ann Scott and Mike Scott of the Namibia Crane Working Group.
By: Dr Ann and Mike Scott
Date: 10 May 2013