Breeding biology and nidology of Oriental skylark (Alauda gulgula) in district Bajaur, Khyber Pakhtunkhwa, Pakistan

A general field survey about Oriental skylark (Alauda gulgula) breeding biology and nest structure (nidology) was carried out during (April, May, June, and July) 2018 and 2019, in district Bajaur. This study was conducted in order to record all the ecological factors that hurdle for the successful breeding of skylark in the study area. For this purpose, we studied 33 nests from egg laying up to the fledging stage. As a result, morphometric measurements of 112 eggs were recorded. Overall eggs were oval dusty white or grey white with black spots and mostly smooth or of somewhat rough texture. Average egg weight 3.0 g, length 2.2 cm, width 3.27 cm and volume 3.65 cm. Likewise explored average clutch size 3.39, incubation period 12.07 days, the number of eggs hatched 3.30 (95.19%), fledged 3.18 (97.34%), and breeding success (89.20%). After normal fledging, the floor of nests was recorded. The shape of nests was entirely round to preferential round; the average nest diameter 9.48±0.8 cm, cup diameter 7.86±0.6 cm, cup depth 6.21±0.5 cm, and nest weight 17.61±0.9 g. The main cause of breeding failure and nest loss was brutal nests and egg destruction by locals and a high rate of land as well avian predators.


Introduction
Oriental skylark (Alauda gulgula) was primarily investigated in Laos during 1997 [1]. It is a small sized bird [2], having a wide dispersal range around Asia including Northern Pakistan, Europe, and Africa. They build their nests on the ground [3,4]. It is the only passerine bird that shows a great association with agricultural farmlands [5,6]. Skylark has eleven to thirteen subspecies [7,8]. They mostly select dry habitats with moderate grasses and agricultural crop-lands for nest construction. Oriental skylark constructs a cup-shaped nest in a shallow depth in the soil from threads and soft grass for breeding purposes [9,10]. Nest construction and incubation are completed by females, but both parents feed the nestlings. The clutch is 2 to 5 eggs, eggs hatch after 12 days. Chicks start flying at the age of 8 to 11 days. They become independent of their parents at the age of 30 days. A single couple makes two to four nesting attempts in a year. The first clutch was laid in early April, and the last broods were fed in late July. The territorial range differs mostly, but the average territories cover an area of 5000-20,000 m 2 . Bird pairs change their territories when there is a change in vegetation and environmental conditions [11,12]. In Western Europe, Oriental skylark population density dropped over the last 30 years due to rapid amplification in farming land [5]. Oriental skylarks were therefore considered a priority species associated with agriculture and cultivated lands for conservation and rehabilitation [12 ]. Among the passerines, more than 70% of nest destruction and failure was that of Oriental skylark. However, nest achievement in different crops was different [12][13][14][15]. The highest population density of Oriental skylark was observed in habitats where crops were more diverse; as crop types offer more suitable habitats for nest construction throughout the breeding period [15]. Oriental skylark does not inhabit vegetation more than 30 to 35 cm in height [15,16]. Little data are available on the ecology of Oriental skylark in Pakistan. The population of Oriental skylark is low in Bajaur due to the loss of habitat and low productivity. So a comprehensive study was conducted about skylark nidology and breeding biology in district Bajaur, Khyber Pakhtunkhwa, Pakistan from April-July 2018 and April-July 2019 respectively.

Field survey
The data were collected on the breeding biology and nidology of Oriental skylark in the study area. Potential sites were surveyed from March to July 2018 and 2019. Oriental skylarks and their nests were searched in the study area using binoculars (7x50mm) and numbered serially for data collection (Fig. 1). GPS coordinates of each nest were recorded (Table 1). Data on breeding season, egg shape, color, texture, etc. were recorded three times a week in the morning and in the evening (Tables 2 & 3, Fig. 2b, 2c, 2d, 2e, 2f). A digital camera was used to photograph the nests, eggs and nestlings. Data were recorded causing minimum disturbance to the habitat, birds, and nest predation following. Vernier caliper was used to measure eggs. A digital scale of 0.1 g to 1000 g was used to weigh eggs, and nests. The volume of eggs was determined by using the following formula No 1: Volume = Kv 2 Where "KV" is constant =0.51, "L" and "W2" are the length and width of skylark eggs respectively. The breeding patterns associated with oriental skylark were determined during the breeding seasons, these patterns were clutch size, incubation period, hatching success, fledging success, and breeding success. The hatching success, fledging success, and overall breeding success were calculated according to Kour [20], by the following formulas; Hatching success % = Number of egg hatched Total egg laid 100 Fledging success % = Number of fledging Number of egg hatched 100 Breeding success % = Number of fledging Total number of egg laid X 100

Statistical analysis
Sample sizes varied for different parameters about breeding biology and nest characterization because we couldn't compare breeding variables for statistical significance due to the low sample size. However, analyzed as mean±standard deviation for both comparison and standard errors by MS Excel (365).

Results
Oriental skylark breeding biology and nidology were explored during the breeding season from April to July 2018 and 2019. Thirty-three nests were investigated. Some nests were explored while being constructed (9 th and 16 th April). The initiation of the breeding period of one skylark pair was recorded on 25 th April, that which lasted up to mid-May, 2018. The remaining breeding pairs were recorded during mid-April, May and June 2018 and 2019 (Table 3 & 4). The clutch size ranged from 2 to 4 eggs (3.39±0.9). The dimensions of eggs varied. All eggs were oval-shaped, the average weight of eggs was 3.00±0.1 g. Similarly, the average eggs length 2.20± 0.04 cm, the average width of the eggs 3.27 ± 0.16 cm 2 and the average volume 3.65±0.07 cm 3 , color grey white with black spots and smooth surface ( Table 2 & Fig. 2b, 2c, 2d); the incubation period 11 to 13 (12.07±0.4) days.
Hatching success was 95.19% probably due to the high predation rate. Nestlings fledged after 9 to 14 days of hatching and left the nests. A fully grown nestling on the 14 th day weighed about 27.5 g (Fig. 2f). The fledging rate was 97.34% of the hatched eggs and the overall breeding success was 89.20% (Table  3). During the nest construction activity, both males and females equally participated in nest construction. Most activities was observed during the early morning by about 8:00 am. In the presence of any observer, the birds remained flying 50 to 100 m from the nest while singing melodious songs (Fig. 2a). A total of 112 eggs, were noted in all 33 nests. Out of 112 eggs 86 were hatched successfully while 26 eggs were destroyed due to mammalian predation and anthropogenic ignorance as shown in (Table 3). Dimensions of each nest were recorded. All the nests were constructed on the ground in natural vegetation and in wheat and barley fields. Outline of the 81.81% nests was completely round while remaining the 18.19% were partially oblong to round. The average external diameter of all the nests was 9.48±0.8 cm, internal (Cup) diameter 7.86±0.6 cm, average cup depth 6.38±0.5 cm, and the average weight of the nesting material 17.61±0.9 g. Nesting material used to construct all the nests mainly consisted of local grasses and dry leaves of trees and local crops including Dichanthiu annulatum (18%). Desmostachya bipinnata (15%), Heteropogon contortus (15%), Cynodon dactylon (18%), Fimbristylis squarrosa, (10%) Phragmites communis (5%), local crops dry leaves (14%), plastic string (2%), contour feathers (2%) and 1% undifferentiated materials as shown in (Table  4).