a b
c
d e f
g h
Some characteristic features of the identified sites include areas relatively devoid of debris and reduced anthropogenic influences such as fishing, movements and motor cycling riding. In areas with these attributes, interviews with ADF team members and field observation also showed a direct relationship of nesting sites to recently exposed soil surface. The PSD of the analysed soils obtained from all the nesting sites ranged between 87% to 96% sandy, (discussion of soil physicochemical sections) giving further credence to nesting in only recently exposed soil surface assertion. Other potential nesting sites candidates were also evaluated and discussed in subsequent section. Soil profiling conducted on the identified nesting sites revealed same elevation with the water bodies or one with slowly increasing elevations.
All identified sites were observed to greater that 10ft above mean sea levels. The relative distance of the shoreline to the farthest identified nesting site is in Diema sea side which was about 22.6m. The area corresponds to only site below mean see levels, absence of debris and higher water energy environment (personal observation). Geo morphological features of an area also influence choice of nesting sites. An area with pockets of water and soil in between similar to ox-bow lake was observed in five locations, two of which were confirmed as nesting sites.
The site shown in Plate 4.8 is reported by the locals to be the most active nesting site. This may not be unconnected with the ease of the hatchlings to be carried into the water bodies. This assertion finds support in Hirth (1971, Carr and Ogren 1960).
4.8.1.7: Nesting Site Soil Physico-chemical
All species of sea turtles exhibit an oviparous reproductive strategy that requires gravid females to return to their natal beaches to lay eggs. While eggs remain buried in the ground during the 45–65-day incubation period, they are exposed to an array of environmental variables that influence the development of eggs and hatchlings (Standora and Spotila (1985), Booth 2006, Burgess et al, 2006). All turtle species censored during the study were either listed vulnerable or endangered on the IUCN Red List of threatened species prompting the conservation and management of suitable nesting sites for these species. Nesting sand physico-chemical parameters were conducted to establish baseline for future management plan. Soil samples collected between 0-60cm (maximum depth of nesting holes) on exposure of surface during ebbing sequence was subjected to physico chemical analysis. The soil profile of yellowish brown was uniform all through. The average physico-chemical parameters obtained for the confirmed and potential nesting sites are as presented in Table 4.18 for comparative evaluation. While detailed physicochemical results is presented in Appendix 4.3.
Table 4.18: Physico-Chemical Properties of Nesting Sites Parameters
Mean of Established Nesting Site
Mean of Potential Nesting Sites
Statistical Difference (P-value at P<0.05)
Reviewed Range for Turtle nests
pH (H2O) @ 24.8oC 4.74±0.31 4.70±0.04 0.935 5-8*
Temperature (0C) 31.8 30.7 0.16 30-32
Elect. Cond. (mS/cm) 1.78±0.08 1.28±0.05 0.001* 0.3-1.0*
Organic Carbon
(g/kg) 3.75±0.20 3.41±0.14 0.066
Moisture Content (%) 15.6 15.3 0.84 15-18*
Sand 89.29±5.20 90.12±4.01 0.837 >85%
Silt 6.90±0.27 5.75±0.06 0.014* <10%
Clay 3.81±0.05 4.13±0.13 0.039 <5
TPH (C8-C40)mg/kg)) <0.05 <0.05 -
THC (mg/kg) <10.00 <10.00 -
Total Nitrogen
(mg/kg) 2.09±0.18 0.57±0.03 0.004*
Chloride (mg/kg) 18.89±0.02 15.65±1.56 0.069 3.75-5.46
Extractable Nitrate
(mg/kg) 0.48±0.08 0.35±0.07 0.104
Ext. Sulphate (mg/kg) 1.76±0.04 0.05±0.02 0.000*
Ext. Phosphate
(mg/kg) 13.31±0.61 13.33±0.48 0.972
Magnesium (mg/kg) 978.00±15.77 522.00±84.15 0.009* 205-363
Potassium (mg/kg) 10,562.00±71.36 9,404.00±451.44 0.044*
Sodium (mg/kg) 5,738.00±228.48 4,294.00±356.40 0.007* 55-145 Calcium (mg/kg) 3,541.00±93.25 2,690.00±105.67 0.001* 148-353 Total Chromium
(mg/kg) 2732.95±434.76 <0.10 -
Total Iron (mg/kg) 16,950.00±653.83 11,487.00±623.74 0.000*
Copper (mg/kg) 55.50±5.05 <0.50 - 0.19-0.52
Lead (mg/kg) 4.75±0.19 3.10±0.11 0.001* 1.05-2.34
Nickel (mg/kg) 21.20±1.59 20.15±1.86 0.496
Arsenic (mg/kg) 7.28±0.34 <0.50 -
Selenium (mg/kg) <0.10 <0.10 -
Molybdenum (mg/kg) 1.25±0.02 0.10±0.00 0.000*
Zinc (mg/kg) 16.61±0.54 6.75±1.06 0.001* 0.38-0.84
Cadmium (mg/kg) <0.10 <0.10 - 0.25-0.52
Mercury (mg/kg) <0.10 <0.10 -
Barium (mg/kg) <2.00 <2.00 -
Aluminum (mg/kg) 37,999.002978.67 33,330.00±1712.66 0.095
Vanadium (mg/kg) 13.62±0.10 2.86±0.06 0.000
Manganese (mg/kg) 267.97 262.75±39.63 0.859
Source: Field Survey 2019
This study establishes novel turtle nesting baseline for physico-chemical parameters in Nigeria.
The pHs of all the nesting soils were acidic. This may not be unconnected with the general leaching effect in Niger Delta (Abii and Nwosu, 2009) that renders most soil acidic. The pH values obtained for both nesting grounds conformed with those obtained by Sükran Yalçın-Özdilek 2005, Bouchard 2000 and Canbolat 2004. Also, no statically significant difference was observed for pH values obtained between the established nesting sites and potential nesting sites.
The temperature values obtained from the established and potential nesting sites compared well with results obtained by Drake 2002, Sükran Yalçın-Özdilek 2005, Girondot 2015 and Zoey, 2017. No statistically significant difference was observed for mean temperature values obtained in the established nesting grounds and potential nesting sites.
Temperature have been reported to be the principal temperature that produces both sexes is called the transitional range (TR) and typically only spans 1–4°C (Wibbels, 2003). In Dermochelys coriacea, the TR is 1°C or less (Binckley et al, 1998 Chevalier et al, 1999).
Temperature during incubation also influences hatching success (Harley et al., 2006). In Lepidochelys olivacea, incubation temperature greater than 35°C result in the death of developing embryos and failure to produce any hatchlings (Valverde et al, 2010).
The moisture content values obtained from the established and potential nesting sites compared well with results obtained by Mcgehee (1990), Ralph et al, (2005), and Matsuzawa et al., (2002).
No statistically significant difference was observed for mean moisture content values obtained in the established nesting grounds (15.6%) and potential nesting sites (15.3%). Moisture content also interacts with temperature to influence hatchling morphology in turtles including the hatching sizes (McGehee 1990) and may also influence the hatchling sex (reviewed by Carthy et al. 2003, Wibbels 2003). Godfrey et al. (1996) found increased production of male hatchlings in green turtle (Chelonia mydas) and leatherback turtle (Dermochelys coriacea) nests during April and May, months with the most rainfall in Suriname. High moisture content decreases gas diffusion throughout the nest (Miller et al., 2003), which can cause egg death if extreme.
Result obtained for moisture content compared favorably with those reported by Brook, (1989), Crain et al., (1995), and Foote, and Sprinkel (1995). Over 90% of the soils in the nesting sites contain sand particles with grain sizes of above 2mm. Salleh et al., (2012) reported that green turtles tend to abort nesting at sites with sands of particle sizes < 1mm. However, large particulate sizes may be preferable in terms of gas exchange between nests and surrounding sand (Mazaris et al., 2008). However, Mortimer (1990) linked the inhibition of green turtle digging and reduction in hatching success to large sand particle sizes. The negative effects large of sand particle size may be caused by high compactness of sand (Chen et al, 2017).
Statistically significant difference at P<0.05 was observed between established and potential nesting sites for Electrical conductivity, total Nitrogen content, Exchangeable sulphate,
Magnesium, Potassium, Sodium, calcium, Iron, lead, Molybdenum, and Zinc. This amounts to about 31% of the total analyzed parameters. These differences could be due to the variation in topography and parent material of the soil. Other parameters showed no statistically significant difference at P>0.05.
4.8.2: Avifauna Species Study Species richness
Species richness is the number of different species represented in an ecological community. A total of twenty-five (25) sighted avian species were censored, as evident in Table 4.18. Some of the sighted species include Nycticorax nycticorax, Casmerodius albus, Phalaropus fulicarius etc. Plate 4.15 is a representative picture of the avian taxa and Table 4.19 is a summarized avian check list.
a. Nycticorax nycticorax b. Casmerodius albus c. Phalaropus fulicarius Plate 4.15: Representative avian taxa censored
Table 4.19: Summarized check list Bird species and Characters Species Frequenc
y
Abundanc e
Behaviou
r Sex
Flight directio n
Altitude
1. Botaurus
stellaris 1 1 F NE 0-50
2. Ardea
cinerea 1 1 F NE 50-75
3. Dendrocygn
a viduata 2 3 R,F,F M,F NE
50-75.50-75,50-75 4. Tachybaptus
ruficollis 1 5 F,F,FL,F F NE,NE.
NE
0-50,50-75.
0-50 5.
Lissotis melanogaste r
1 2 FL SE 0-50,50-75
6. Ardea
goliath 1 4 R.F,F,FL.
F,F F,F NE,NW.
NE
0-5-,50-75,50-75.
50-75,50-75
7. Ardea 2 2 F.F,F M NE. SW 0-50.
Species Frequenc y
Abundanc e
Behaviou
r Sex
Flight directio n
Altitude
cinerea 75,50-75
8. Porphyrio
porphyria 1 1 R, R,R F SW. NE 75.
50-75,50-75
9. Podica
senegalensis 1 1 F,FL SW 50-75,50-75
10. Rostratula
benghalensis 1 1 FL SW 75&ABOV
E 11. Actophilorni
s africanus 1 1 FL SW 75 &
ABOVE 12. Microparra
capensis 1 6 F,R. F.F F,M,
M
NE. NE.
NE
0-50,0-50.
50-75. O-50 13.
Anastomus lamelligerus
• 2 1 F. FL. F,F NE. SW 0-50. 50-75.
0-5-,0-5- 14. Scopus
umbretta 2 6 R. F NE. SW 0-50. 0-50
15. Anas crecca 1 4 FL. FL. R NE. SW 75.
50-75 16. s Nycticorax
nycticorax 3 2 F. R. R NE, NE 0-50. 50-75,
50-75
17. Bubulcus ibis 2 3 FL. R SW. NE 50-75. 0-50
18. Casmerodius
albus 3 3
R,R,F,FL.
FL.FL.
FL
M,M NE,NE.
NE
50,50,575. 0-50
19. Calidris alba 1 2 R,R SW 50-75,50-75
20. Sterna caspia 2 7 R,FL. RF.
FL,R M NE.NE
NE,NE
50,575,575. 0-50. 50-75,0-50
21. Ardenna
grisea 1 3 F,F,FL.
F,F,F NE. SW
0-50,50-75.
50. 0-50,0-50 22. Hydrobates
leucorhous 1 6 R,R M NE,SW.
SW,NE 50-75,50-75 23. Phalaropus
fulicarius 2 4 R. R,R,FL NE. NE 0-50,50-75.
50-75,50-75 24. Stercorarius
longicaudus 1 4 FL. FL.
FL F NE. NE 75.
50-75,50-75 25. Stercorarius
pomarinus 1 4 F. F NE 50-75
Source: Field Survey 2019
Species Abundance of Birds
A total of 77 individuals were censored across the counting and observation stations. The findings revealed that Nycticorax nycticorax, Casmerodius albus, and Phalaropus fulicarius accounted for about 40% the total counts.
Species Frequency of Birds
Bird species frequency was also evaluated. Nycticorax nycticorax, Casmerodius albus, Dendrocygna viduata, Ardea cinerea, Anastomus lamelligerus, Scopus umbretta, Bubulcus ibis, Hydroprogne caspia, Phalaropus fulicarius were more frequent. Noteworthy is the presence of these species in at least two different habitats making them highly adaptable to wider food source as food availability in habitat varies. Those observed in only one habitat are highly specific and enjoy territorial dominance. However, they encounter declining population and range when their habitat is challenged with threats such as climate change and other weather-related issues. Climate has played a key role in shaping the life histories of species (Parmesan 2006). Rapid human‐induced climate changes, such as those experienced today, and the effects this will have on the evolution and ecology of wildlife species are not well understood (Parmesan 2006, Dawson et al. 2011). Migratory animals, for example, are highly mobile, which could make them more resilient to climate change if they are able to shift their ranges or their phenology to track suitable climate. In fact, long‐distance migration may have evolved in response to prehistoric climate change (Louchart 2008). On the other hand, migrants may be more vulnerable because their annual climatic and ecological requirements are complex and span vast distances. They are exposed to a wide range of climatic conditions, and climate changes at migratory, winter, or summer locations could influence survival, reproductive success, or ecological cues used to optimize migratory timing ( Studds and Marra 2007, Gienapp et al. 2012, Cohen et al. 2015).
Bird Behaviour
Three behavioural tendencies were evaluated at the time of censoring. They were feeding, resting and flight. A total of twenty individuals were observed in flight while 23 were observed resting. Thirty-two individuals were observed feeding. In terms of habitats, nine individuals each were observed during feeding and on flight as against 11 resting. Botaurus stellaris, Ardea cinerea and Stercorarius pomarinus were always observed feeding, Porphyrio porphyria, Calidris alba and Hydrobates leucorhous were observed always resting. Lissotis melanogaster, Rostratula benghalensis and Actophilornis africanus on the other hand was always on flight. De bushing would adversely impact these species observed as resting always.
Flight direction
Flight direction was equally observed and evaluated. The birds were observed flying in three main directions. Ten individuals were observed flying in the NE direction as against one flying in the North westerly direction. Seven individuals were observed flying in the south westerly
direction for which all three individuals of Podica senegalensis, Rostratula benghalensis and Actophilornis africanus were remarkably seen flying in the south westerly direction only.
Nevertheless, there was no observable peculiarity in flight direction among other bird species.
Sex evaluation
The bright colouration of the male was used as discriminatory character. A total of 15 individuals were identified as belonging to any of male or female. Seven were female and eight were male. No defined flocking pattern was observed either among the individuals or among the specific sexes in anyone habitats.
Altitude
Flight altitude was also evaluated. The findings showed that one individual was flying within 0-50m altitude. Significantly, 19 individuals were observed within the 50-75m range. On the other hand, 2 were seen flying above 75m. Other species observed in the 50-75 and above the 75m active while in flight. Conversely, there was no species observed exclusively within the 0-50m range. Species within this altitudinal range seems attracted to feeding and resting. Since species in this range were also observed in the 50-75m range, it is most likely that the height of the trees in the habitat is determining factors. They perch on the trees after long flight duration to rest or when they needed food. A strong correlation coefficient of 0.79 was obtained between altitude and bird behaviour in this study.
Species migration
Some avian species are known to migrate. Avian migration is either regular or irregular (Nomadic interruption or invasions) seasonal movement between north and south. Avian migration is usually driven by food, habitat and changes in weather conditions. These movements are usually between breeding and wintering grounds (veen et al., 2014). In Nigeria as in other countries in the Northern hemisphere, migratory birds commence this movement between February, March and April to warmer areas and return between August, September and October to winter grounds. Migratory movement often results in high mortality and predation. Details are shown below in Table 4.20 and Plate 4.16 are pictures some of the censored migratory species.
Table 4.20: Details of Migratory Species
Species Local
Name Nesting Grounds Breeding season Major threats Conservation actions (IUCN/Local)
Ardea cinerea Tree tops and branches
Mid-February –end of
May Habitat loss. Colony protection
Nycticorax
nycticorax Trees or ground
(reed beds) March - September Habitat loss Colony protection
Casmerodius albus Pinabo
Marshes, ponds, shores, mud flats, trees or shrubs near water
Mid-December - January Habitat degradation and loss
Colony protection/ control of disturbance and
vegetation management Botaurus stellaris reedbed edge March -June habitat alteration
Dendrocygna
viduata Round, reed over
water,trees
According to location &
rainy season
Susceptible to avian botulism, influenza. Human disturbance
Invasive species control or prevention, Subject to ex-situ conservation, In-Place Education Subject to recent education and awareness programmes, Included in international legislation, Subject to any international
management/trade controls.
Tachybaptus
ruficollis Shallow water March -July
transformation of wetlands by destruction, pollution or recreation
Monitoring and protection should be introduced to ensure the destruction of wetland habitats is mitigated and where possible prevented.
Ardea goliath
reeds, bushes, trees or even on rocks or large tree stumps
Rainy season
Action Recovery Plan, Systematic monitoring scheme, Conservation sites identified, occurs in at least one protected area, Invasive species control or prevention,
Species Local
Name Nesting Grounds Breeding season Major threats Conservation actions (IUCN/Local)
successfully reintroduced or introduced benignly, Subject to ex-situ conservation, Subject to recent education and awareness programmes, included in international legislation, Subject to any international management / trade controls
Ardea cinerea Trees, reed-bed, cliffs, bushes
Mid-February _ end of May
habitat alteration, hunting, and predation at nesting colonies, Timber harvesting
Colony protection
Anastomus
lamelligerus
Nests are typically built in sedge meadows, grasslands, brush thickets, or in woods near a pond.
Rainy season
The species is threatened by habitat loss, entanglement in fishing lines and
environmental pollution, it also suffers from hunting, poaching and the destruction of breeding colonies by villagers
Action Recovery Plan, Systematic monitoring scheme, Invasive species control or prevention, ex-situ conservation, Subject to recent education and awareness programmes, Included in international legislation,
Subject to any
international management / trade controls
Anas crecca
Nests are typically built in sedge meadows, grasslands, brush thickets, or in woods near a pond.
late-February onwards (peaking March-April)
lowland habitat loss and degradation, upland habitat loss due to afforestation and other land-use changes, disturbance from human recreational activities
Action Recovery Plan, Systematic monitoring scheme, Conservation sites identified Conservation sites identified, Invasive species control or
Species Local
Name Nesting Grounds Breeding season Major threats Conservation actions (IUCN/Local)
Calidris alba
sandy beaches of inland lakes, prairie potholes, and saline or alkaline flats
mid-July to mid-August
species is threatened by the degradation and loss of wetland habitats through environmental pollution, reduced river flows and human disturbance
Action Recovery Plan, Systematic monitoring scheme, Conservation sites identified Conservation sites identified, Invasive species control or prevention etc.
Sterna caspia
sandy, muddy, or pebbly shores or areas with little vegetation on islands
late May and early June Biological resource a, intrusions & disturbance
Invasive species control or prevention
Ardenna grisea Underground September to November
By-catch in drift nets and gillnets
The species is monitored at some sites and has been extensively studied in parts of its range. Some breeding grounds are protected and have benefited from the eradication of introduced predators.
Breeding habitat
alteration/degradation (due to human activities or introduced herbivores);
Introduced predators in breeding habitat;
Mutton birding – hunting of nesting birds, for human consumption.
*IUCN Status of the censored migratory species revealed all as Least Concern (LC)
Plate 4.16: Migratory Species of the study area (a - c)