Distribution of Avian Ecological Groups from Different Water Levels Habitats During Autumn Migration Provide Way Forward to Preserve the Diversity of Birds in Reserve

The study was conducted to understand the relationship between ecological groups of birds, habitat water level in wetlands


INTRODUCTION
I n the development of China's economy, the impact on wetlands and birds living in them is increasing, and the problems of wetland area reduction, fragmentation, functional degradation and environmental quality decline are becoming more and more prominent, resulting in a significant decline in the species and number of birds.
For birds, habitat is the environmental type occupied by individuals, populations or communities in a certain stage of life history, providing places for their various life activities.Previous studies on wetland habitat mainly focused on environmental factors such as topography, geomorphology, soil, vegetation type, water source, climate and vegetation factors such as plant community composition, plants' spatial structure, seasonal variations and life period (Evans et al., 2009;David et al., 2016;Xie et al., 2019).
However, there are few studies on habitat change due to water changes and water level types preferred by different birds.The migration period is an important stage in the life cycle of birds (Zou et al., 2012;Liechti et al., 2015).A key platform for energy supplies and rest for migratory birds is represented by stopover sites (Alan et al., 2013;Norevik et al., 2017).A complete understanding of the spatial distribution of migratory birds in wetlands

O n l i n e F i r s t A r t i c l e
during autumn, will help to improve the protective actions.
Zhalong National Nature Reserve (Zhalong) is one of the biggest reserves with wetland area in Northeast China.Since the 1990s, the wetlands in Zhalong have registered a dynamic degradation due to water level fluctuations and unbalanced spatial distribution of water resources (Wang et al., 2006;Wu and Zou, 2011;Luo et al., 2014).These were caused by natural disturbances and human activities, including drought caused by reduced rain fall, annual wild fire during springtime, fishing in summer, reed harvest in winter and all kinds of wetland exploitation activities (Wang et al., 2010).In 2001, Zhalong had established a new water management control in order to provide water supplies in the dry years.By 2017, 2.585 million m 3 of water was transfused into the Zhalong Nature Reserve maintaining the marsh wetland ecosystem functional.
Studies have also shown that artificially controlled water levels changed the natural fluctuation of water levels in Shengjin Lake, resulting in a significant impact on the habitat of local wintering water birds.For example, due to excessive human influence, the water level is too high and there are few exposed grass beaches and mud beaches, so the utilization resources of local overwintering waterfowls are extremely rare (Wang et al., 2010).The diversity of avian communities at different water levels and with different spatial distribution have registered significant differences before and after irrigation, every year.Hence, this research studied the spatial distribution of the avian communities at different water level environments, during the autumn period, in Zhalong Nature Reserve.However, the spatial distribution of the avian communities during water level fluctuations remained constant (Liu et al., 2015).This study will lead not only to the improvement of bird communities habitat during autumn, but it will also serve as a scientific reference for irrigation schemes of wetland ecosystems.

Site description
Zhalong (46°52´−47°32´N, 123°47´−124°37´E) lies at 26 km to the Southeast of Qiqihar city in Heilongjiang Province, China.In 1992, it was listed as a Ramsar "wetland of international importance" (especially as waterfowl habitat) (Wang et al., 2015;Zou et al., 2016).Proper location map with GPS readings is shown in Figure 1.The region belongs to the continental semiarid and monsoon climate.The total area of this reserve is 2100 km 2 with an average elevation of 144 m above sea level.The reed marshes cover 80%−90% of the reserve area, while Carex swamp (Carex pseudoeuraica (sedge) swamp and bulrush swamp), meadows, grasslands and farmlands occupy the remaining area (Wu et al., 2016(Wu et al., , 2017)).The wetland habitats are suitable stopovers for birds during autumn migration.Also, the reed marshes in the wetlands represent a primary economic resource for local people.

Data collection
Field investigations were carried out from August 2005 to October 2009, in Zhalong (Qiqihar city), Dangnai and Laomachang (Daqing city).By using linetransect sampling, square sampling, circle sampling, and point sampling methods, data of different bird species and their population numbers were collected from 101 sample areas in different habitat types (53 sample areas were from reed marsh area, 14 from water areas, 10 from Carex pseudocuraica marsh, 9 from meadows, 8 from farmlands, and 7 from open forest).Among them, the point sampling and square sampling methods were used for the investigation of bubble marshes and the use of the method was different due to the number of birds and the area and shape of the bubble marsh (square sampling method, photo and video method were used to investigate those bubble marshes with large number of birds and no statistics).Two to four observation sites were selected for each bubble and the observation time of each site was 10-15

O n l i n e F i r s t A r t i c l e
min.The reed marsh area, Carex pseudocuraica (sedge) marsh, meadows and farmlands were observed by the linetransect sampling method.The length of sample line was 2 km and the unilateral width was about 100 ~ 1000 m.The actual length and unilateral width change due to the actual hydrology and observation objects.The actual survey was conducted once a month.7-10 days each time, tried to select the same or similar monthly and sunny days for the survey.Surveyed twice a day in the morning and evening, specific observation recording times varied depending on the local sunrise time and light visibility, and in principle the local sunrise h to 9 am and 2 h before sunset were preferred (Zou et al., 2012) and 8x20 mm binoculars and 20-60 x 60 mm single-tube telescopes (spotting scope) were used to collect the data.

Avian ecological groups
According to this research from eight avian ecological groups in the world, six of them were present in Zhalong reserve.These are natatores (N), grallatores (G), terrestores (T), raptatores (R), scansores (S) and passeres (P).The water level was defined as water depth and classified based on the clustering results of 39 waterfowl species recorded by this survey and the measurement using steel tape.Considering the leg length of all waterfowl species, three clusters were generated: 2.81-5.73cm, 10.36-15.24cm and 22.93-28.61cm as shown in Figure 2 (Zou et al., 2012) and the maximum value was regarded as a threshold value of water level gradient.In this study, wetland environment with a water level of 0 cm was used as a specific value of water depth.The threshold values on water levels were divided into four classes, namely 0 cm, 5 cm (5.73 cm), 15 cm (15.24 cm) and 30 cm (28.61 cm).So, water levels were classified into five water level gradients, such as: 0 cm water level (no water) (WL0), 0-5 cm water level (WL1), 5-15 cm water level (WL2), 15-30 cm water level (WL3) and more than 30 cm water level (WL4), as shown in Table I.

Data analysis
The collected data were analyzed using SPSS software (version-11.5)statistical program.First, analyzed the data of different avian ecological groups monitored at different water level habitats (five water level gradients and six habitat types), by counting total numbers of avian population and density during autumn migration.Chisquare test (χ2 test) was used to analyze the correlation between the uses of different avian ecological groups of different habitat types at different water levels.Finally, it was comprehensively analyzed for habitat preference of different avian ecological groups.

Species component and dominant avian ecological groups
A total of 79 species of birds belonging to 32 families of 13 orders was recorded during the study period as shown in Table II, representing 41.36% of the total avian species observed at Zhalong. Figure 3 shows that species composition of six avian ecological groups was grallatores= passeres > natatores > raptatores > scansores = terrestores, representing 12.65%, while the population numbers were passeres > grallatores > natatores > raptatores > terrestores > scansores, summing, 11.24%, respectively.The passeres, grallatores, and natatores were the threemain avian ecological groups observed during autumn migration in Zhalong as shown in Figure 4, accounting for 87% as species richness and population numbers.Use of different water level habitats Chi-square test showed a significant difference (p < 0.01) among the uses of six avian ecological groups of different water level habitats as shown in Table III.More than 80% of passeres and terrestores population preferred habitats with no water surface (WL0) and water depth higher than 30 cm (WL4), while more than 70% of grallatores population had strongly preferred water level habitats with depths higher than 30 cm (WL4) followed by natatores (more than 90%), and only more than 3% of them preferred habitats with no water surface (WL0).More than 60% of the raptatores population preferred water level habitats with water depths higher than 30 cm (WL4) and more than 20% preferred habitats with a water depth of 15-30 cm (WL3).100% of the scansores population preferred habitats with no water surface (WL0).All the six avian ecological groups preferred habitats with no water surface (WL0) as well as habitats with water depth higher than 30 cm (WL4); the latter was the mutual preferred habitat of the three dominant avian ecological groups.

O n l i n e F i r s t A r t i c l e
Distribution of Avian Ecological Groups

Use of different habitat types
Chi-square test results showed a significant difference (p < 0.01) among the use of avian ecological groups and habitat types as shown in Table IV.More than 75% of the Passere population preferred reed marsh and forest belts, while less among them selected water bodies.More than 80% of the Grallatores population preferred water bodies and reed marsh, while less population preferred the farmland.More than 98% of the Natatores preferred water bodies and reed marsh.More than 90% of the Raptatores population preferred reed marsh and more than 94% of the Terre stores preferred reed marsh and farmland.Only the Scan sores population preferred forest belts.During autumn migration, the six avian ecological groups chose all habitat types, except meadow steppes.However, reed marsh and water bodies were the most preferred habitat types by the three dominant avian ecological groups.

O n l i n e F i r s t A r t i c l e
A. Zulfiqar et al.For details of water levels see Table III.

Habitat preference
During autumn migration, six avian ecological groups had different habitat preferences regarding water levels and habitat types as shown in Table V.The habitat preference of passeres was forest belts with no water surface (WL0), reed marsh and water bodies with water deeper than 30 cm (WL4).The grallatores preferred water bodies and reed marsh with water depth higher than 30 cm (WL4) and farmland with no water surface (WL0).The natatores preferred water bodies and reed marsh with higher than 30 cm water depth (WL4).The raptatores preferred reed marsh with water depth higher than 15 cm (WL4 > WL3), while the terrestores preferred reed marsh with water depth higher than 30 cm (WL4) and farmland with no water surface (WL0).Only the scan sores preferred forest belts with no water surface (WL0).
From the collected data it can be concluded that water bodies with higher than 30 cm water depth (WL4), reed marsh with more than 15 cm water depth (WL4 and WL3), farmland with no water surface, and forest belts with no water surface were the dominant habitats chosen by these six avian ecological groups, during autumn migration.The reed marsh with more than 30 cm water depth (WL4) was the mutually preferred habitat by the three dominant avian ecological groups.This showed the existence of an overlap distribution area for the three dominant avian ecological groups, represented by the reed marsh area with more than 30 cm water depth (WL4).Similarly, water bodies with more than 30 cm water depth (WL4) were another overlap distribution area for the passere and grallatore populations.

O n l i n e F i r s t A r t i c l e
Distribution of Avian Ecological Groups 7 Dominant avian ecological groups had close relationships with the dominant vegetation environment.In Zhalong, wetland environment with reed marsh and water bodies is the absolute dominant vegetation environment.As a result, the grallatores and natatores were the two main avian ecological groups depending on the wetland environment.The passeres were the main avian ecological group in the Northeast district, China (Zhao, 1988).
This research showed a consistent result.The dominant vegetation environment and geographical region are the two important influencing factors of the distribution of dominant avian ecological groups during autumn migration in Zhalong.

DISCUSSION
The results indicate that Passeriformes, Anseriformes and Charadriiformes were the main species in bird communities, followed by Gruiformes, Ciconiiformes and Falconiformes orders.The Zhalong National Nature Reserve shelters all the six ecological groups' occurring in China.The passeres had the largest number of birds among the six avian ecological groups, followed by the grallatores and natatores.This fact is closely related with the unique wetland environmental characteristics of the region.The previous studies have shown that the bird community structure was abundant with the Passeriformes being dominant for non-waterfowl and the Charadriiformes dominant for waterfowl in Zhalong (Guan et al., 2009).The area has a complete wetland ecosystem that provides a good habitat for the grallatores and natatores.At the same time, the passeres was the main bird population observed in the northeast, by this survey.As species components and dominant avian ecological groups, the richness of species recorded by this study was far more abundant than the previous records (Guan, 2009).There might be two reasons causing the difference.One of the potential reasons could be the sampling areas number.The sampling areas for this research were 101, which were by far more than the previous research with three line-transect sampling areas.This is probably the main reason that generated the significant difference.Another reason is the studied area which in this survey is the entire reserve area, while the previous research observed only one part of the reserve.

Effect of different water levels on avian distribution
During the autumn migration period, different ecological groups have shown evident preferences for different water levels (Zou et al., 2016).Large waders such as the Gruiformes and Ciconiiformes were inhabited in deepwater environments while some small wading birds preferred no water surface environment, such as the Charadriiformes.The passeres and terrestores selected both waterless and aquatic environments due to their specific traits.Because of the high frequency of human activities such as fishing, the natatores chose to live in the deep-water area during autumn.Scan sores preferred to choose the waterless environment.Numerous studies have shown that 68 waterfowl species having different measures in length and size, exhibit different needs for food types, habitats and water depths.The difference in water levels is particularly significant for wetland habitats, especially food resources and habitat environments.Therefore, each waterfowl has its optimum water level and available water level requirements.

Effect of different habitat types on avian distribution
This study results suggest that during the autumn migration period, different ecological groups showed significant differences in choosing different habitats except for the Scan sores.Water bodies were chosen mainly by the Grallatores and natatores, followed by the passeres, the reed marsh mainly used by the raptatores and terrestores, followed by the natatores and passeres.The meadow steppes were mainly chosen by the passeres and raptatores while farmland was mainly used by the grallatores and terrestores, followed by the passeres and natatores.The forest belts mainly had sheltered the Scan sores, followed by the passeres and raptatores.Considering the chosen locations of birds in different habitats, the choice of ecological groups showed overlapping and differentiation.In addition, the water bodies, reed marsh and farmlands were the main habitats of ecological communities, providing breeding and resting places for birds.There is a certain competitive relationship between rare animals and ordinary wild animals in the utilization of wetland resources during the migration period.The research on the influence of environmental factors such as water level on the habitat of autumn migration can help to take more effective protection measures for rare animals.

Effect of habitat preferences on avian distribution
The natural ecosystem of Zhalong National Nature Reserve provides a high-quality living place for all kind of birds.The reed marsh habitats with different water levels are ideal habitats for large waders such as the cranes.There are open lakes providing a good source of food and resting places for all kinds of avians like Anseriformes, Podicipediformes and Charadriiformes.The passeres have a wide range of activities and they are distributed in the reed marsh with deep water levels and forest belts.Different water levels affect the growth and distribution of wetland organisms, type, structure and composition of wetlands.Thus, different water levels and habitat types are

O n l i n e F i r s t A r t i c l e
A. Zulfiqar et al.
particularly important for bird habitat selection.

CONCLUSION
In Zhalong Nature Reserve, a total of 79 bird species belonging to 32 families and 13 orders were observed during autumn migration, including six avian ecological groups namely grallatores, passeres, natatores, raptatores, scan sores and terrestores.The passeres, grallatores and natatores were the three dominant avian ecological groups during autumn migration; and reed marsh with more than 30 cm water depth (WL4) and water bodies with more than 30 cm water depth (WL4) were their most preferred habitats.Different avian ecological groups had a different preference for water levels (P < 0.01) and habitat types (P < 0.01).Further analysis showed that reed marsh and water bodies with deep water depth were the main overlap habitat of different avian ecological groups especially the dominant groups, dominant wetland vegetation environment and unique geographical region were the key influencing factors of avian ecological group's spatial distribution.Based on this research, reed marsh and water bodies need more attention during autumn migration to preserve the avian diversity of the reserve.
In general, birds of different ecological groups have different requirements for habitat, and the same species also has different characteristics for habitat selection in different spaces, seasons and life periods.Appropriate water level changes will produce relatively diverse vegetation environment and habitat types, which will help to provide various types of habitats for different bird species.Therefore, moderate artificial regulation of water level can contribute to the construction of bird habitats and the scientific management of birds in Zhalong area.According to the distribution characteristics of birds in the protected area, the target birds are determined to restore the species, and the appropriate living space of birds is created based on the observed results.

O n l i n e F i r s t A r t i c l e
Distribution of Avian Ecological Groups

Fig. 3 .
Fig. 3. Species composition (A and B) of six avian ecological groups.