Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 April 2020 | 12(5): 15565–15571
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
doi: https://doi.org/10.11609/jott.5366.12.5.15565-15571
#5366 | Received 28 August 2019 | Final
received 13 February 2020 | Finally accepted 04 April 2020
Habitat structure determines the
abundance of the Endangered Sharpe’s Longclaw Macronyx
sharpei (Aves: Passeriformes: Motacillidae)
at Timau montane grasslands in central Kenya
Dominic Kimani 1, Muchane Muchai 2,
Johnstone Kimanzi 3, Joseph Mwangi 4,
Wanyoike Wamiti 5,
Samuel Bakari 6, Bernhard Walter 7 & Peter Njoroge
8
1,2,3 Department
of Wildlife Management, University of Eldoret, P.O. Box 1125-30100, Eldoret,
Kenya.
1,4,5,8
Zoology Department, National Museums of Kenya, P.O. Box 40658-00100, Nairobi,
Kenya.
2 Department of
Clinical Studies, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya.
6 BirdLife International, African Secretariat, P.O. Box
3502-00100, Nairobi, Kenya.
7 Biological
Station Guetersloh and Bielefeld e.V.
Niederheide 63 33659 Bielefeld, Germany.
1 dkk4.kimani@gmail.com
(corresponding author), 2 mmuchaim@yahoo.com, 3 kimanzijo@gmail.com, 4
mwamujos@yahoo.com,
5 wwamiti@gmail.com,
6 bakarisamuel@gmail.com, 7 Bernhard.Walter@biostationgt-bi.de,
8 peter.njoroge2306@gmail.com
Editor: Simon Dowell,
Chester Zoo, UK. Date
of publication: 26 April 2020 (online & print)
Citation:
Kimani, D., M. Muchai, J. Kimanzi,
J. Mwangi, W. Wamiti, S. Bakari, B. Walter & P.
Njoroge (2020). Habitat structure determines the abundance of the
Endangered Sharpe’s Longclaw Macronyx sharpei (Aves: Passeriformes: Motacillidae)
at Timau montane grasslands in central Kenya. Journal of Threatened Taxa 12(5): 15565–15571. https://doi.org/10.11609/jott.5366.12.5.15565-15571
Copyright: © Kimani et al. 2020. Creative
Commons Attribution 4.0 International License.
JoTT allows unrestricted use, reproduction,
and distribution of this article in any medium by providing adequate credit to
the author(s) and the source of publication.
Funding: Nature and Biodiversity Conservation Union (NABU) Germany; African
Bird Club; National Research Fund Kenya (NRF).
Competing interests: The authors declare no competing interests.
Author details: Dominic Kimani (DK) is the lead ornithologist for Kipeto Energy PLC (KEP). Prior to joining
KEP, he worked as a research scientist at National Museums of Kenya. Dominic
has an MSc degree in Wildlife Ecology from University of Eldoret. He has
undertaken extensive avian research and conservation for over 20
years. Dr. Muchane Muchai (MM) is currently the Head of
Wildlife Section and Senior Lecturer, Department of Clinical Studies, Faculty
of Veterinary Medicine, University of Nairobi. Dr. Muchai is currently teaching graduate and post graduate students and
conducting research focusing on biodiversity management and conservation as
well as food security. Bernhard Walter (BW) is a senior biologist and the Chief executive officer at the
Biological station in Bielefeld and Gutersloh in Germany. He has been
involved in many avian research projects. He is an avid ornithologist with over
3-decade experience. Dr. Peter Njoroge (PN) has been actively engaged in biodiversity research for the last
24 years especially research on avian species. He has published over 50
journal articles on conservation, avian ecology and environment-related
issues. Dr. Joseph Mwangi (JM) is currently the Kenya country Coordinator for the African Crane
Conservation Program, a partnership program between the
Endangered Wildlife Trust (EWT) and International Crane Foundation (ICF). He
spearheads coordination and implementation of the Kenya Crane and Wetland
Conservation Project that works to conserve the endangered Grey Crowned Crane. Wanyoike Wamiti (WW) is a Research Scientist at the National
Museums of Kenya and a final year PhD candidate (Biology of Conservation) at
the University of Nairobi conducting research on the ecology of the Endangered
Grey Crowned Crane at Lake Ol’ Bolossat. He has a two decades experience of Kenyan
ornithology. Samuel Bakari (SB) is a tropical ecologist. He holds a Master of Science degree from
the University of Groningen, the Netherlands and a bachelors from the
University of Nairobi. He has worked on grassland birds for over 15 years, Bakari currently works for BirdLife International in coordinating vulture conservation in Africa. Dr. Johnstone Kimanzi (JK) is a Spatial Ecologist interested in applying GIS and Remote
Sensing tools to model complex ecological systems and solve biodiversity conservation and wildlife management problems. He is
currently a Senior Lecturer and Head of the Department of Wildlife Management
at the University of Eldoret, Kenya.
Author contribution: Study
design (DK, MM,JK, JM, BW & PN); Data collection (DK, JM, MM, JK, BW, SB
& WW); Data analysis (DK, JM, JK & MM); Manuscript write up (DK, JM,
MM, JK, BW& PN).
Acknowledgements: This study would not have been possible without the
unconditional permission and support from the management and staff of Marania farm. In
particular, we are deeply indebted to Jamie Murray, the general manager for all
logistical assistance. The financial
support received from NABU (BirdLife Germany) through
Werner Schroder, African Bird Club, David Fox Family, Patrick Mboso, Late Sarah Higgins, and National Research Fund
(Kenya) is highly appreciated. Our
appreciation goes to National Museums of Kenya for allowing time for the first
author to be away from duty. We are
sincerely grateful to University of Eldoret for supervising this research. Johana Kamau’s dedication to data collection
and perseverance to the chilly weather is not taken for granted. Boniface Mwangi is treasured for his time
helping with the statistical analysis and production of the study area
map. Many thanks to Dr.
Kariuki Ndang’ang’a for
invaluable help in the field, the staff of Wildlife Department for assistance
to first author. We also wish to thank Drs. Rosie
Trevelyan and Kevin Wallace of Tropical Biology Association for valuable
comments on the manuscript.
Abstract: Understanding the habitat
selection and structure of a species is critical for developing evidence-centered conservation actions. Sharpe’s Longclaw Macronyx
sharpei, a passerine bird endemic to Kenya, is
threatened by reductions in habitat size and quality that have left it
inhabiting a small and highly fragmented range.
From January to June 2016 we investigated the abundance and density of
Sharpe’s Longclaw in Marania farm located in Meru
county in the northern sector of Mt. Kenya, where no previous study had been
done. Population abundance and density
were determined using the flush and count method. We observed that these birds were exclusively
found in grasslands, being most abundant in habitats of short grass with
tussocks, and less so in areas with tall grass.
This habitat specificity indicates a key requirement for survival of
Sharpe’s Longclaw populations in this area.
We recommend surveys in and around Marania
farm to determine the distribution of suitable habitats for this species, and
that the farm be designated an Important Bird Area. Further studies should also focus on
determining the intensity of grazing that is compatible with conservation of
Sharpe’s Longclaw populations.
Keywords: Conservation, density, endemic,
grasslands, passerine bird, population.
Introduction
Abundance of bird species is largely influenced by the
spatial and temporal distribution of key resources (McCain 2009). Elevation and slope affect vegetation
structure, site productivity, distribution, composition, and secondary biotic
interactions (Girma et al. 2017). The conservation of Sharpe’s Longclaw (Image
1) requires a detailed understanding of population sizes and distribution, and
habitat quality and availability. This
endemic and endangered species is restricted to grasslands at 1,800–3,500 m
altitude (BirdLife International 2018). It has been reported at higher elevations,
but this has not been confirmed (Borghesio et al.
2013). Much of past research has been concentrated in the Kinangop grasslands in the southern parts of Nyandarua County (Muchai 1998; Muchai et al. 2002; Ndang’ang’a
et al. 2002; Mwangi et al. 2012; Borghesio et al.
2013). The species occurs at low
densities throughout its range (BirdLife
International 2015). In Kinangop grasslands, Ndang’ang’a
et al. (2002) recorded a density of 1.2 individuals/ha while Muchai et al. (2002) and Mwangi et al. (2012) found an
overall mean density of 0.85±0.21 individuals/ha and 1.24 ± 0.15
individuals/ha, respectively. At Lake Ol’ Bolossat, Wamiti
et al. (2008) recorded a density of (0.004–0.06 individuals/ha). There are few precise breeding records (Keith
et al. 1992). The highland grasslands
that are strongholds for Sharpe’s Longclaw (Muchai
1998; Muchai et al. 2002; Ndang’ang’a
et al. 2002; Borghesio et al. 2013) also provide
nesting, feeding, and breeding habitats for the eastern African endemic and
near-threatened Jackson’s Widowbird Euplectes
jacksoni, the regionally threatened Long-tailed
Widowbird E. progne, and the
Afro-tropical highland biome-restricted species Hunter’s Cisticola Cisticola hunteri (Bennun & Njoroge 1999).
The Timau high altitude
grasslands in Kenya have recently undergone significant reduction, primarily
due to habitat conversion to crop lands (Kimani et al. 2015). The alarming decline of local grassland
habitat is linked to land sub-division within family units and sale of land
parcels, resulting in native grassland loss and fragmentation. The local people living in the Kenyan
highlands whose livelihood mainly revolves around small-scale farming play a
large role in habitat fragmentation (Muchai 1998; Ndang’ang’a et al. 2002; Kimani et al. 2015). The main threat to native grassland habitat
is conversion, especially through cultivation and establishment of woodlots of
exotic species (Muchai 1998; Muchai
et al. 2002; Borghesio et al. 2013). These factors have exacerbated the pressure
on highland grassland biodiversity, and the establishment of large-scale
farming for commercial crops that are more profitable than livestock has also
contributed to reduction of native grassland habitats.
Lack of appropriate information on the population
status of Sharpe’s Longclaw prevents efficient management of the habitats
necessary to guide conservation efforts.
Collection of such information on population size, abundance, and
density are important when deciding where to allocate resources in conservation
and research activities, and to provide empirical data to evaluate existing
management strategies. These data are
essential for the IUCN Red List of Threatened Species assessments. The overall objective of this study was to
investigate population abundance and density of Sharpe’s Longclaw in different
habitat types in Marania farm, following reports that
the species was present there. A
detailed understanding of population size, spatial distribution and demographic
trends will inform future management decisions and conservation interventions.
MATERIALS AND METHODS
The population of Sharpe’s Longclaw was studied in Marania farm, Meru County (0.080–0.070 0N and
37.458–37.367 0E), part of the northern section of Mt. Kenya that
offers a previously unstudied fragmented population of the species. Marania farm is an
approximately 2,580ha privately owned farm bordering Mt. Kenya National Park on
the north-eastern side. The elevation of
Marania farm grasslands where this study was carried
out ranged from 2400 to 2800 m. In Marania farm, rearing of livestock (sheep and beef cattle)
that forage in the native grasslands is controlled by paddocks, although the
animals are supplemented with hay during the dry seasons. There is also natural vegetation in the
valleys and hill tops.
Grasslands in this farm cover an area of 865ha while
the rest is under cultivation and interspersed with natural and planted
forests. The farm has crops such as
wheat, canola, peas, maize, and a small portion of mixed crops. They also practice animal husbandry. During the study, there were approximately
150 cattle grazing in the study area, over 400 sheep, and about 20 horses. The average annual rainfall in the area
ranges 380–2,500 mm with a bimodal rainfall pattern in March–May and
October–December (Gakuubi & Wanzala
2012).
Sharpe’s Longclaw is a monogamous, sedentary species
restricted to high altitude, open, short grasslands. It is territorial and insectivorous, feeding
particularly on grasshoppers and beetles.
Birds live in permanent groups of two–seven individuals depending on the
quality of their habitat (Muchai 1998; Muchai et al. 2002).
Sampling Design and Census
During the first month of the study (20 January–20
February 2016), a survey of Marania farm was done to
determine appropriate study plots through purposive sampling. The study area was divided into six grassland
plots (Figure 1) measuring an average of 2.25 ± 0.12 (SD) ha (range 2.21–2.45
ha). Three of the plots were
characterized as short grass with dense tussocks (SGWDT) and the other three as
tall grass (TG) following Muchai et al. (1998). The plots were separated by different
matrices with either natural forest, farm cultivation or plantation
forests. Grass height at plots was
classified as SGWDT and ranged between 10–20 cm while those of TG were 30cm and
above, following design employed by Muchai (1998).
The plots were monitored for a period of five months
(February–June 2016). Sharpe’s Longclaw
(SLC) is known to breed during the onset of rains or shortly after rains
(Kimani et al. 2015). The study partly
coincided with the breeding season but, only for a short period between April
and May (Muchai 1998). This was done deliberately to ensure the
breeding population was present. Due to
the limitation of time, the study lasted only five months, in which February
and March were dry while April–June were wet months. Censuses were conducted at each study plot at
different times of the day (spread in three 4-hour long observation periods;
06.00–10.00 h, 10.00–14.00 h, 14.00–18.00 h) to give a spread of data on a
spatial and temporal spread throughout the day.
Each study plot was intensively searched once every week; 20 censuses
were undertaken in each of the six study plots.
Study plots were intensively searched using a flush-out and count method
(Muchai 1998; Muchai et al.
2002) where two people dragged a 50m rope on opposite ends to flush out the
birds for easier sighting. Flushed out
Sharpe’s Longclaws were recorded, and the position they flew to was noted to
avoid double counting. The original
position of the bird was marked using a hand-held global positioning system
unit (Garmin etrex 20).
Statistical analysis
Bird abundance in grasslands was examined in relation
to plot size, grass height and presence/absence of tussocks using a generalized
linear model via Poisson regression (Table 1).
Abundance per plot was calculated as the total number of individuals
counted divided by the number of sessions the birds were counted in that
plot. Mean density was calculated as the
mean abundance divided by the size in hectares of the plot. Generalized linear model via Poisson
regression was used to determine which of the independent variables explained
population abundance in the grassland habitat.
Results
Mean abundance
The mean ± SE abundance in short grass with dense
tussocks (SGWDT) was 4.53 ± 0.30 while in tall grass (TG) it was 2.23 ±
0.29. Figure 2 illustrates a significant
difference in mean abundance between SGWDT and TG (P= 0.01, df
=40, t = -6.95).
Determinants of Sharpe’s Longclaw abundance
Three variables were the significant determinants:
grass height (β =0.021, P=0.050), tussocks presence/absence (β=1.101, P=0.001)
and interaction of grass height and tussocks presence /absence (β= -0.059,
P<0.001) (Table 1). The equation of the fitted model was:
Abundance = 1.188+0.021 grass height +1.101 tussocks
presence/absence -0.059 grass height* tussocks presence/absence.
Mean density
As birds did not occur in non-grassland habitats, the
six grassland plots had a mean density of 0.78±0. 37SD. The mean density was 2.00 ±0.06 and 1.04
±0.07 Sharpe’s Longclaw per ha for SGWDT and TG, respectively (Figure 3). There was a significant difference between
mean densities in SGWDT and TG (Mann-Whitney W-test = 89.0, df
= 42, P = 0.0001).
Discussion
Sharpe’s Longclaw population abundance and densities
had a clear association with habitat variables.
The birds revealed a strong preference for areas of short grass with
dense tussocks. Areas of tall grass were
less preferred, and birds occurred there at lower densities. This preference for a specific grassland
habitat matches that reported in studies by Muchai et
al. (1998, 2002) and Mwangi et al. (2012) in Kinangop
grasslands.
It has been observed that many endemic bird species
have high densities on grazed pastures due to co-evolution with large grazing
mammals, for instance the Chestnut-collared Longspur Calcarius
ornatus (Kantrud 1981;
Knopf & Rupert 1996). Low grazing
intensity results in long grass and bush encroachment, while intense grazing
destroys grass tussocks (Borghesio et al. 2013). Muchai et al.
(2002) found that the persistence of Sharpe’s Longclaw in the grasslands
depends on intermediate levels of disturbance, resulting from grazing by
mammalian herbivores. Our findings are
consistent with those of Muchai et al. (2002), in
that all the areas where we found Sharpe’s Longclaw had grazing, especially by
cattle. Although we did not have
adequate data to verify a relationship with various grazers, we suggest that
the stocking rate might be more important than the species, as shown in Sliwinskia & Koper (2015). Besides domestic animals, wild antelopes
(Bushbucks Tragelaphus scriptus,
Duiker Neotrragus moschatus)
were regularly observed during the survey period, while Cape Buffaloes Syncerus caffer and
African Elephant Loxodonta africana from
the neighboring Mount Kenya National Park sometimes
were reported to break fences and graze as well (unpublished data). These wild animals might also influence
grassland height (Ogada et al. 2008) and ultimately
Sharpe’s Longclaw, but the data we had did not allow for testing of their
effects on grassland height and structure.
Field observations showed that Sharpe’s Longclaw used tussocks mainly to
rest during the hottest part of the day, which also agrees with observations by
Muchai et al. (2002).
The height of grass plays an overriding role in
determining habitat segregation and food specialization among bird species
(Fisher & Davis 2011). Interspecific
competitive exclusion is believed to be the main mechanism explaining
occurrence or specialization of birds in grassland vegetation of different
heights (McDonald 2017). Therefore, at
least within grassland systems, mosaics of short and longer vegetation are
likely to hold the maximum benefit for many farmland birds (Benton et al.
2003). Maphisa
et al. (2017) argue that a combination of grass height and cover is more
essential than just grass height alone or grass cover alone. It would be plausible to argue that Sharpe’s
Longclaw would probably spend more time being vigilant to detect predators
other than carrying out other essential life process in tall grass due to tall
grass obscuring their visibility (Muchai et al.
2002).
Although effect of patch size was not investigated in
this study, results by Mwangi et al. (2012) showed large patches of grassland
that are favoured by Sharpe’s Longclaw compared to small ones. Consistent with this finding, Marania farm, being a large grassland under the same
management, is a potential Sharpe’s Longclaw conservation site if properly
managed. A year-long study is
recommended to understand the breeding strategies that are exhibited by the
Sharpe’s Longclaw. In addition, our
findings indicated that tall grass was equally good for Jackson’s Widowbird Euplectes jacksoni,
a Near Threatened species. This species
had over 40 nests in the tall grasses.
Large patches of grassland would be ideal for conservation of various
species in different categories of threats.
Conclusion and Recommendations
The findings of this study demonstrate that Timau grasslands still hold suitable and extensive habitat
for the endemic and Endangered Sharpe’s Longclaw. The study established that the mean
population abundance was higher for short grass with dense tussocks compared
with tall grass. Mean density was also
higher in habitat of short grass with dense tussocks. In comparison to previous studies, it was
acknowledged that Marania appeared better than other
parts, like Kinangop grassland, previously thought to
be the world stronghold of the species.
Sharpe’s Longclaw is threatened by a very rapid and
continuing reduction in the extent and quality of its habitat (Birdlife
2018). It is, therefore, imperative for
conservationists to collaborate with farms such as Marania
farm to adopt suitable management practices due to the role they play in
conservation of this grassland-dependent bird species. Surveys in neighbouring farms should also be
carried out to determine abundance and the extent of population distribution of
Sharpe’s Longclaw, and to assess the
suitability of its habitat. This will be
critical in guiding a discussion with the landowners on the merits of
designating the farm/grasslands the status of BirdLife
International Important Bird Area (IBA).
This would be an important task that can be undertaken by the Sharpe’s
Longclaw Working Group. One way of
recognizing the role Marania farm play in conserving
Sharpe’s Longclaw would be designating the area as an IBA to allow easy
marketing of the area as a key tourist attraction site (avi-tourism)
for Meru County. Being an endemic
species that is becoming rare in its formerly known areas like Kinangop, good marketing would take keen bird watchers to Marania farm where it would be easy to find and perhaps photograph
the Sharpe’s Longclaw in its natural habitat.
Further research needs to be undertaken for both wet
and dry seasons in order to understand if the species is affected by seasonal
dynamics. Further research is also
needed to shed light on the most appropriate conservation measures. More information is required to determine the
best grazing regimes optimal for Sharpe’s Longclaw with economic benefits for
easier adoption.
Table 1. Generalized linear models via Poisson
regression examining the relationship between grass height (GLHT), tussock
presence/absence (TUPA) and their interaction (TUPA * GLHT) on Sharpe’s
Longclaw abundance in Marania farm grasslands.
Parameter |
Estimate ± SE |
95% confidence limits |
Wald chi-square |
Df |
Sig. |
Intercept |
1.19 ± 0.18 |
0.83, 1.55 |
42.43 |
1 |
< 0.01 |
Grass height |
0.02± 0.01 |
-0.00, 0.04 |
3.84 |
1 |
0.05 |
Tussock presence/absence |
1.10± 0.34 |
0.427, 1.78 |
10.25 |
1 |
0.001 |
TUPA * GLHT |
-.059 ± 0.01 |
-0.086, -0.03 |
18.52 |
1 |
< 0.001 |
For
figures & image - - click here
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