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Behavioral Ecology
Behavioral Ecology
Write a scientific paper on the feeding behavioural ecology of the Tasmanian Native hen within two contrasting habitats. Review, correct and improve original submission.
Assessment item 1
Assignment 1
Value: 40%
Due date: 04-Sep-2015
Return date: 25-Sep-2015
Resubmission date: 25-Oct-2015
Length: 3000 words, plus abstract, references, tables etc
Task
Each student is to write a scientific paper on the feeding behavioural ecology of a single species of
bird in two contrasting habitats. Specifically you must:
Select your species . Choose a species that is wild (only under exceptional circumstances
will domestic or caged birds be allowed in this assignment), easy to observe, abundant, and
local to your area.
Choose your habitat types . Spend some time observing your species and determine where
it feeds. Then select two habitat types where it feeds-one might be its preferred spot, the
other might be a marginal habitat. You must be able to collect behavioural data at both sites.
Some possible habitat contrasts might be: edges versus centre; roadside versus bush;
parkland versus bush; dam versus river; degraded (weedy) bush versus intact bush;
introduced habitat (like blackberries or a garden) versus native habitat.
Make behavioural observations . Your behavioural observations may take the form of
foraging, anti-predator vigilance, or conspecific interactions (territoriality). Your
observational choice will be specific to the species that you choose. You will have to
determine what types of behaviour you will be recording (feeds/min., antagonistic bouts,
alarm calls, etc.). Your task is to gather exactly the same sorts of data from your two sites
and then compare them.
Analyse observations . Using your statistical knowledge, analyse the behavioural data that
you have collected. Do not worry if your results are negative; that is, you find no difference
between your two habitats. There is plenty to write up even for this sort of result.
Write a scientific paper . Write up your data in a Harvard Citation Style scientific paper.
Use the Behavioral Ecology Citation Style as detailed in Scientific Section of the Subject
Outline. It is strongly recommended that you have a third party proof read your paper before
submission AND make sure that every reference you cite in the paper is in the references list
at the end. There is nothing that indicates sloppy research more than sloppy referencing
technique. Remember, too, that when you are writing your discussion, stick to behavioural
ecology explanations (ultimate not proximate reasoning). Also, the last thing you should
write is the abstract.
Rationale
This assignment involves the production of a scientific report and will assess your ability to design and implement your own behavioural study. It will assess your ability to collect primary behavioural data, determine your understanding of ultimate causes of behaviour, assess your ability to write a scientific paper and apply statistical analyses to raw data, and enable you to research and apply subject components to a specific species.
Feeding behavioural ecology of the Tasmanian native hen Tribonyx mortierii in two contrasting habitats
A.M. Dugand
Abstract
Habitat use by the Tasmanian native hen Trybonyx mortierii searching for food within two contrasting habitats was compared in rural North-west Tasmania, site selection included habitat within an urban location, the other within an intense production rural location. The Independent Sampling method was chosen with the aim to collect data from both individuals from a pair, and from all individuals from a small group (seven individuals); to combine results for a more detailed average value. Habitat use was investigated through data collection from foraging activity and associated responses to distinct constraints at each habitat type, these data were analysed using a paired t-Test to determine any variance, the results of which identify that foraging behaviours differ, so too does the social structure that theoretically affect individual fitness.
Introduction
Belonging to the rail family, the Tasmanian native hen Trybonyx mortierii is one of fifteen species that occur in Australia, of which six can be described as gallinules (Ridpath 1964) being heavy built with a shorter bill and powerful legs. Presumed to have originated from the Australian mainland Black-tailed native hen Tribonyx ventralis, the Tasmanian native hen is a large gallinule that stands at approximately 45cm in height, with dull brownish-green feathering with a white patch on its flank, not conspicuous on juveniles, a short greenish bill with yellowing towards the tip, and with bright red eyes. It is a highly dispersive flightless bird with robust legs that can run for short distances up to 45 kms per hour (Ridpath 1972a), during which can change direction quickly, often with wings outwardly spread and various angles to assist with balance. The tail is short and dark and typically held erect and can be tilted slightly forward during dispersal bouts. Tail flicking is a common behaviour and generally occurs as part of a warning signal to others, and is largely associated with routine scanning during foraging activities.
Native hens are social and are often found in pairs or small groups up to seven, and often make loud distinctive rasping calls with several birds joining in unison. Usually feeding at dawn and dusk on short juvenile grass shoots, herbs and seed, will also forage opportunistically during daylight hours close to refuge habitat. Insects are consumed by chicks, adults have been observed hunting small skinks to provide to chicks that are also consumed by adults (Peter Tonelli, pers. com.) Preferring more open country surrounding water courses and grazed pasture, the Tasmanian native hen has also adapted to an urban environment with a high tolerance to pedestrian and vehicle traffic.
Figure 1. Tasmanian native hen with chick.
The Tasmanian native hen is a group-territorial cooperative breeder displaying frequent mate-sharing by both sexes (Putland & Goldizen 2001). In the Tasmanian native hen population, there is an excess of males among immature birds. Permanent breeding groups are established, sometimes of pairs and sometimes of trios; the commonest type of trio consists of two brothers and an unrelated female (Maynard Smith, J & Ridpath MG 1972). Breeding commences in July to December and females typically lay five or six eggs and more up to 10 is not uncommon, in a good season can produce more than one clutch. Various breeding strategies can be undertaken due in part to the higher ratio of males to females ensuing in approximately fifty percent of small groups consisting of only one female resulting in a polygamous system (Ridpath 1972b), the remainder are monogamous with juveniles take part in raising and protection of siblings. Due to limited habitat availability, in part due to high adult survivorship, dispersal is often delayed (Goldizen, Putlan & Robertson, 2002).
Tasmanian native hen (Figure 1) populations are largely controlled by natural processes and fall prey to Eagles, juveniles are taken by Swamp harriers, eggs are frequently taken be ravens and quolls, with occasional roadkill occurring closer to urban areas. Food availability whilst abundant comes with risks associated with a preference for partially grazed grasses within a high production landscape with diverse and frequent cropping rotations close to habitat fringes. This study aims to investigate foraging strategy differences within two contrasting habitats; site one is just north of the headwaters of Skeleton Creek in North Motton (Figure 2), which begins at Leven Hill (elevation 320m), a narrow tributary surrounded by small paddocks that are in close proximity to the riparian zone with a mix of native grasses (Poa sp.) and introduced pasture grasses, the system is dammed multiple time along its 8 km reach, meanders through undulating farmland heading north where it joins the Leven River Estuary 3.5 kms west of Nicholsons Point, site 2 (Figure3). Site two is within an urban landscape largely unaltered with retention of undisturbed natural vegetation that spans forty meters in width from the high water mark is some areas with a combination of native (Poa sp.) and introduced landscaped grasses (Couch sp) on the edges closest to urban infrastructure.
| Habitat refuges |
| Foraging areas |
Figure 2. Tasmanian native hen habitat at Skeleton Creek, North Motton. Riparian area surrounded by intensive cropping, dairy and cattle grazing.
Methods
Study areas
The study was conducted during the commencement of breeding season over a three week period in August 2015, prior to which an investigation into the appropriate selection of two contrasting habitats was conducted to ensure data collection could be achieved without disturbance to individuals or individuals within small groups, of a species known for high levels of anti-predator alertness displays, followed by rapid retreat to a nearby roosting site for protection. The Tasmanian native hen habitat preference is varied where individual or small groups can often be seen along waterbodies with nearby natural vegetation consisting of rushes and sedges in close proximity to partially grazed pasture grasses common in rotational stock grazing, or landscaped street grasses.
| Habitat refuges |
| Foraging areas |
Figure 3. Tasmanian native hen habitat at Nicholson Point, Leven River Estuary, Ulverstone, Tasmania.
The Leven River Estuary between the Bass Highway overpass and the Western Line railway bridge, is a reach of 1.3kms comprising of upper storey Paperbark (Melaleuca sp), Sheoak (Allocasuarina sp) and Wattle (Acacia sp) with Tussock grass (Poa sp) and sedge (Isolepis sp) ground cover that is largely intact and varies in width averaging thirty metres, includes areas of landscaped grasses up to ten metres in width. The eastern bank was selected due to ease of access without disturbance to individuals; preliminary observations were conducted to determine the number of individuals, pairs or small groups that occurred at the site, when foraging activities were undertaken, and for what duration.
Data collection
The Independent Sampling method was chosen with the aim to collect data from both individuals from a pair, and from all individuals from a small group (seven individuals); to combine results for a more detailed average value. The sampling effort was conducted daily for durations of 30 minutes at each of the two sites commencing at 7:45am, and again late afternoon commencing at 4:15pm approx. Where unfavourable weather conditions impacted on sampling effort, random sampling events were conducted during the day for the same duration and locations in an effort to maintain daily consistency.
Using a stopwatch, mounted binoculars and two crowd counters, observations of an individual within a pair or group were monitored and recorded for durations of 60 second intervals, for a period of 30 minutes from an average distance of 50 metres approx. from a fixed concealed position; within this timeframe three activities were recorded to include the number of pecks and tail flicks, also the number of times the individual stopped to perform an anti-predator alert scan. During a sampling event where possible, each individual in a pair was sampled equally. In the event one or both individuals dispersed to nearby habitat following a significant predator response occurrence, the sampling would resume when one or both returned, this typically occurred in less than one minutes, if longer, the data collection effort would be abandoned, and resumed later in the day. During sampling events that consisted of a small group, random individuals were selected attempting to sample all within the group, therefore less sampling undertaken per individual as compared to pair sampling.
Typically weather conditions vary during August with many changes occurring in any 24 hour period. As such, planned sampling efforts on many occasions were abandoned due to only one or no individuals foraging at one or both survey sites, therefore adjusting the original protocol to extend the field time-frame was necessary to gain multiple 60 second data capture sessions.
The Purple Swamphen Porphyrio porphyrio also cohabitate with the Tasmanian native hen though generally confined to swamps, damp grasslands and farm dams. This highly dispersive rail is clumsy in flight with large powerful legs often seen nesting on reeds, and like the Tasmanian native hen can swim despite not having webbed feet. Bouts of territoriality between both species were included in the observation data collection and recorded at each occurrence, noting cause and effect.
Statistical analysis
The initial analyses were conducted for three dominant behavioural characteristics within two contrasting habitats, two of which were selected for a more detailed investigation with data prepared to conduct a paired t-Test. To enable statistical testing, data were square-root transformed prior to analysis.
Results
General results
Two sampling hours per day for a duration of 10 sample days (N = 10) with 50 percent dedicated to each habitat type resulted in an individual within an estuary system achieving per minute mean of 101.9 pecking rate, with standard error of 0.82. During this time displaying a per minute tail flick mean 1.35 with a standard error of 0.25, as compared to an individual within an agricultural system achieving a per minute mean 73.5 pecking rate with standard error of 0.43 and a per minute tail flick mean of 14.9 with a standard error of 0.86.
Results – Creek system, Agricultural
A small group up to seven individuals were sighted usually in pairs along both banks of the dam (Figure 2), During frequent survey efforts, two individuals were observed chasing each other agitatedly, followed by composed foraging, during this fast paced agitated chase, the lead hen would veer sharply at great speed in altered directions with one wing upturned, then switch to the other to attain balance, as well as a combination of high pitched calls and grunts, with the follower close behind. Foraging bouts were less resourceful than compared with hens extant in estuaries; predator vigilance was more frequent as was the tail flicking motion that increased with the onset of a sudden change in alertness levels, during dispersal the tail was erect and tilted forward until such time as the running ceased. Hens in agricultural zones were more exposed to predators, less adapted to human interaction, consequently appeared to display more alert signals than that of estuary hens, therefore estimated less efficient in terms of forage gain (Figure 4).
Figure 4. Activity during a 60 second foraging session, noting estuary hens attaining higher nutrient efficiency.
Results – Estuary, Urban
Pairs of native hens were sighted frequently along various sections of the study site, up to four pairs that kept clear defined territories where individuals did not overlap at any time (Figure 3). Foraging was interrupted temporarily by human activity that included pedestrian and vehicle movement, during which one individual would flee prompting the other to remain on alert for up to 30 seconds, soon afterwards the hen would return and resume foraging. Hens were rarely disturbed by local residents or domestic pets, however during data capture events it was necessary to arrive early, allowing for the hens to settle prior to commencement.
During the survey, other behavioural characteristics were also noted, of which most were very momentary. For this reason collating behavioural data based on intensity and frequency in the form of a rank system more appropriate was recorded, and for what duration (Table 1).
Table 1. Ranks describing the intensity of activity according to observed behaviour and duration within a 60 second sample interval
| Score | Behaviour | Duration (s) |
| 1 | Foraging activity generally occurring within a small area usually in pairs consisting of rapid regular pecking (between 80 and 90 pecks per minute average) | 50 |
| 2 | Tail flick occurs in most instances simultaneously with anti-predator alert pose with head held erect in readiness to disperse with tail flicks erect and tilted forward | 8 |
| 3 | Anti-predator alert pose occurs throughout the foraging activity at regular rapid intervals, occasionally held for longer | 6 |
| 4 | Running took place in response to sudden movement from another bird, rabbit, cat or vehicle that approached the foraging area, sometimes aggression towards another hen | 1.5 |
| 5 | Stretching occurs at random consisting of extending one leg behind the body and holding the posture for up to 3 seconds at any one time | 0.9 |
| 6 | Preen was undertaken by only one individual at any one time and with in-between pecking bouts | 0.6 |
| 7 | Resting with legs tucked under body, head remained erect and semi-alert | 0.3 |
Discussion
Tasmanian native hens forage close to refuge habitat and are rarely seen in open grasslands, when seen, usually in pairs within metres of each other, and often taking turns in anti-predator vigilance. Smaller groups of up to seven can be seen more frequently in agricultural zones associated with a larger areas than that of estuary zones, and will be active in defence of a territory and will do so vigorously by running after an intruder during which loud calls, grunts, pecking (striking) and kicking displays occur, sometimes causing injury. The investigation commenced during the early stages of the breeding period and it is likely that some of the territory defence is associated with the breeding season.
Foraging efficiency comparison
Foraging comprises of pecking vigorously into the soil substrate (with bill slightly open which then grasps the seed), where by acquiring fine herbage, seed and a few invertebrates, often exceeding 100 pecks per minute (Figure 4). These feeding items are widely and more or less evenly distributed and the hens move steadily, grazing over most of their territory during the day (Ridpath 1971), interrupted by rising of the head quickly to determine that it is safe to continue, this activity usually lasting only one or two second before vigorous pecking resumes.
Foraging efficiency differed between the two habitats, individuals in the agricultural zones spent more time in a vigilant state with each alert pose lasting longer in duration than that of individuals in the estuary habitat, in some instances up to ten seconds. The vigilant state of individuals in the estuary habitat whilst more frequent, was short lived in most instances lasting one or two seconds, allowing for more foraging efficiency overall (Figure 4). Due to varied weather conditions during August, native hens in open more vulnerable agricultural zones, were not always foraging early morning or late afternoon as was predictable in the estuary habitat, therefore inspections of the site at random during daylight hours was required to attain balanced time allocation of sampling per habitat.
Tail Flick behaviour
Tails flicking also occurs and sometimes simultaneously whilst the head was erect, though in some instances would occur during pecking. Alarm responses of native hens are diverse, to include a slightly raised head whilst observing a predator, will tilt the head slightly depending on where the predator is, for example airborne or offset of view, at this point the tail flick may develop with head stretched and elevated, still watching the predator, whilst the tail is erect and flicking sporadically in a vertical position, each tail flick is fast, usually less than a second. Tail flicking was rapid during the alert pose in all native hens sampled in the agricultural zone. In some instances tail flicking did not occur at all in individuals within the estuary habitat, on occasions would occur during pecking activity. A dampened alarm call may be heard in response to a ground predator, this soft low call can often be hard to detect though appeared distinctive to the native hens family group.
A wing flick can occur and is more so associated with the presence of human, dog and wedge-tailed eagle Aquila audax, all deemed more dangerous to adult native hens (Ridpath 1971). The wing flick action is also very rapid and appears to be similar to that of a comparable species that do fly, and usually in response to aerial predators. Goshawks are frequently seen in the vicinity of Skeleton Creek study site, together with the return of the migrating Swamp harrier. A sharp alarm call is used to warn others of imminent danger and can be heard at greater distances than the lower deep grunt call.
Alert responses
An alarm walk is distinct, with tail cocked and head up, the bird walks rapidly towards a refuge site during which remains on high alert to possible danger, should this potential danger increase, the individual may increase the walk pace to a run meanwhile continues to watch the predator. This posture may intensify according to threat, and may vary to a faster sprint, with head up and tails still cocked.
On reaching refuge native hens remain alert and simultaneously watch the predator by peering through the vegetation in readiness to relocate if required. On one occasion, two individuals swam swiftly to the opposite bank of a dam, one remaining submerges momentarily.
Vocalisation appears varied consisting of low deep grunts which appeared to be related to either a response to the presence of a ground predator, or part of territorial displays with a range of frequencies. Physical position also altered in response to different perceived threats and the severity of a particular threat at that time.
Locomotion
As a flightless bird, the native hen relies entirely on its powerful legs for locomotion, with its distinct pace, during which each foot is lifted high off the ground and then extends it well frontward, which is unlike most birds that hop or which gait is less intense. During running, the body tends to lean forward and lunges with long strides and with a tendency to flap wings during high speed events, this motion appears to assist with balance should sharp turns be required. Despite not having webbed feet, native hens swim, so too do chicks, generally in response to predator evasion. Running occurred more within an agricultural zone that the estuary habitat, presumed due to a more exposed landscape.
Figure 5. Tasmanian native hen non foraging activity noting a high level of preening undertaken within an agricultural zone as compared to that of an urban site.
Maintenance
Stretching was evident during most sampling efforts, during which an individual would bring forward one leg and wing simultaneously for one or two seconds followed by a restful pose. Stretching movement occurred evenly within both habitats (Figure 5). Resting was recorded on two occasions during which one individual folded both legs under the body similar to a chicken roosting, retaining this posture for less than five minutes which was followed by routine foraging. Other studies record that native hens usually sleep standing on both legs with head tucked over the back, often huddled together and usually in the same location for several successive nights (Ridpath 1972). Preening was recorded more so in an agricultural zone possibly due to more individuals sampled based on a dominance of groups within that habitat type.
Acknowledgement
Thanks to local Naturalist Peter Tonelli for his knowledge insight into Tasmanian endemic avifauna species particularly local to the North-west region, and for the image in Figure 1.
References
Goldizen, AW, Putland, DA & Robertson, KA 2002, Dispersal strategies in Tasmanian native hens (Gallinula mortierii) Behavioural Ecology, Vol. 13, No 3: 328-356
Maynard Smith, J & Ridpath MG, Wife Sharing in the Tasmanian native Hen, Tribonyx mortierii: A Case of Kin Selection? The American Naturalist Vol. 106, No. 950 (Jul. – Aug., 1972), pp. 447-45
Putland, DA & Goldizen, AW 2001, Family dynasties in the Tasmanian native hen (Gallinula mortierii). Behav Ecol Sociobiol 51:25-32.
Ridpath , MG 1964. The Tasmanian native hen, Tribonyx mortierii, pp. 346-350. Australian Natural History, Vol. xiv, No 11. CSIRO Hobart Tas.
Ridpath, MG 1972a. The Tasmanian native hen, Tribonyx mortierii. I. Paterns in behaviour. CSIRO Wildl Res 17:1-51.
Ridpath, MG 1972b. The Tasmanian native hen, Tribonyx mortierii.II. The individual, the group, the population. CSIRO Wildl Res 17:53-90.
Feeding behavioural ecology of the Tasmanian native hen
Tribonyx mortierii in two contrasting habitats
A.M. Dugand
Abstract
Habitat use by the Tasmanian native hen Trybonyx mortierii searching for food within two contrasting habitats was compared in rural North-west Tasmania, site selection included habitat within an urban location, the other within an intense production rural location. The Independent Sampling method was chosen with the aim to collect data from both individuals from a pair, and from all individuals from a small group (seven individuals); to combine results for a more detailed average value. Habitat use was investigated through data collection from foraging activity and associated responses to distinct constraints at each habitat type, these data were analysed using a paired t-Test to determine any variance, the results of which identify that foraging behaviours differ, so too does the social structure that theoretically affect individual
Introduction
Belonging to the rail family, the Tasmanian native hen Trybonyx mortierii is one of fifteen species that occur in Australia, of which six can be described as gallinules (Ridpath 1964) being heavy bui lt with a shorter bill and powerful legs. Presumed to have originated from the Australian mainland Black-tailed native hen Tribonyxventralis, the Tasmanian native hen is a large gallinule that stands at approximately 45cm in height, with dull brownish-green feathering with a white patch on its flank, not conspicuous on juveniles, a short greenish bill with yellowing towards the tip, and with bright red eyes. It is a highly dispersive flightless bird with robust legs that can run for short distances up to 45 km per hour (Ridpath 1972a), during which it can change direction quickly, often with wings outwardly spread and various angles to assist with balance. The tail is short and dark and typically held erect and can be tilted slightly forward during dispersal bouts. Tail flicking is a common behaviour and generally occurs as part of a warning signal to others, and is largely associated with routine scanning during foraging activities.
Native hens are social and are often found in pairs or small groups up to seven, and often make loud distinctive rasping calls with several birds joining in unison. Usually feeding at dawn and dusk on short juvenile grass shoots, herbs and seed, will also forage opportunistically during daylight hours close to refuge habitat. Insects are consumed by chicks, adults may hunt small
skinks to provide to chicks that are also consumed by adults (Peter Tonelli, pers. com.) Preferring more open country surrounding water courses and grazed pasture, the Tasmanian native hen has also adapted to an urban environment with a high tolerance to pedestrian and vehicle traffic.
Figure 1. Tasmanian native hen with chick.
The Tasmanian native hen is a group-territorial cooperative breeder displaying frequent mate- sharing by both sexes (Putland & Goldizen 2001). In the Tasmanian native hen population, there is an excess of males among immature birds. Permanent breeding groups are established, sometimes of pairs and sometimes of trios; the commonest type of trio consists of two brothers and an unrelated female (Maynard Smith, & Ridpath 1972). Breeding commences in July to December and females typically lay five or six eggs and up to 10 is not uncommon, in a good season females can produce more than one clutch.1972b), the remainder are monogamous with juveniles taking? part in raising and protection of siblings. Due to limited habitat availability, in part due to high adult survivorship, dispersal is often delayed (Goldizen, Putlan & Robertson, 2002).
Tasmanian native hen (Figure 1) populations are largely controlled by natural processes and adults may fall prey to Eagles; juveniles are taken by Swamp harriers; eggs are frequently taken be ravens and quolls; with occasional roadkill occurring closer to urban areas (references?). Food whilst abundant, comes with risks associated with a preference for partially grazed grasses within a high production landscape with diverse and frequent cropping rotations close to habitat fringes. This study aims to investigate foraging strategy differences within two contrasting habitats;
Figure 2. Tasmanian native hen habitat at Skeleton Creek, North Motton. Riparian area surrounded by intensive cropping, dairy and cattle grazing.
Methods
Study areas
The study was conducted during the commencement of breeding season overathree week period in August 2015., A preliminary investigation was conducted to ensure data collection could be achieved without disturbance to individuals or individuals within small groups, of a species known for high levels of anti-predator alertness displays, followed by rapid retreat to a nearby roosting site for protection. The Tasmanian native hen habitat preference is varied where individual or small groups can often be seen along waterbodies with nearby natural vegetation consisting of rushes and sedges in close proximity to partially grazed pasture grasses common in rotational stock grazing, or landscaped street grasses.
Figure 3. Tasmanian native hen habitat at Nicholson Point, Leven River Estuary, Ulverstone, Tasmania.
The Leven River Estuary between the Bass Highway overpass and the Western Line railway bridge, is a reach of 1.3kms comprising of upper storey Paperbark (Melaleuca sp), Sheoak (Allocasuarina sp) and Wattle (Acacia sp) with Tussock grass (Poa sp) and sedge (Isolepis sp) ground cover that is largely intact and varies in width, averaging thirty metres, includes areas of landscaped grasses up to ten metres in width. The eastern bank was selected due to ease of access without disturbance to individuals; preliminary observations were conducted to determine the number of individuals, pairs or small groups that occurred at the site, when foraging activities were undertaken, and for what duration.
Data collection
The Independent Sampling method was chosen with the aim to collect data from both individuals from a pair, and from all individuals from asmall group (seven individuals); to combine results for a more detailed average value. sampling was conducted daily of 30 minutes at each of the two sites, commencing at 7:45am, and again late afternoon commencing at 4:15pm approx. Where unfavourable weather conditions impacted on sampling effort, random sampling events were conducted during the day for the same duration and locations in an effort to maintain daily consistency.
Using a stopwatch, mounted binoculars and two crowd counters, observations of an individual within a pair or group were monitored and recorded for durations of 60 second intervals, for a period of 30 minutes from an average distance of approx. 50 metres from a fixed concealed position. wActivities recorded included the number of pecks and tail flicks, and the number of times the individual stopped to perform an anti-predator alert scan. During a sampling event, where possible, each individual in a pair was sampled equally. In the event one or both individuals dispersed to nearby habitat following a significant predator response occurrence, the sampling would resume when one or both returned, this typically occurred in less than one minute. If longer, the data collection effort was abandoned, and resumed later in the day. During sampling events that consisted of a small group, random individuals were selected attempting to sample all within the group, therefore less sampling undertaken per individual as compared to pair sampling.
Typically, weather conditions vary during August with many changes occurring in any 24 hour period. As such, planned sampling efforts on many occasions were abandoned due to only one or no individuals foraging at one or both survey sites, therefore the original protocol was adjusted to extend the field time-frame was necessary to gain multiple 60 second data capture sessions.
The Purple Swamphen Porphyrio porphyrio also cohabitate with the Tasmanian native hen though generally confined to swamps, damp grasslands and farm dams. This highly dispersive rail is clumsy in flight with large powerful legs often seen nesting on reeds, and like the Tasmanian native hen can swim despite not having webbed feet. Bouts of territoriality between both species were included in the observation data collection and recorded at each occurrence,
Statistical analysis
Initial analyses were conducted for three dominant behavioural characteristics within two contrasting habitats, two of which were selected for a more detailed investigation with data prepared to conduct a paired t-Test. To enable statistical testing, datawere square-root transformed prior to analysis.
Results
General results
Two sampling hours per day for a duration of 10 sample days (N = 10) with 50 percent dedicated to each habitat type resulted in an individual within an estuary system achieving per minute mean of
Results – Creek system, Agricultural
A small group up to
Figure 4. Activity during a 60 second foraging session, noting estuary hens attaining higher nutrient efficiency.
Results
During the survey, other behavioural characteristics were also noted, of which most were very momentary. Forthis reason collating behavioural databased on intensity and frequency in the form of a rank system more appropriate was recorded, and for what duration (Table 1).
Table 1. Ranks describing the intensity of activity according to observed behaviourand duration within a 60 second sample interval
Discussion
Tasmanian native hens forage close to refuge habitat and are rarely seen in open grasslands, when seen, usually in pairs within metres of each other, and often taking turns in anti -predator vigilance. Smaller groups of up to seven can be seen more frequently in agricultural zones associated with a larger areas than that of estuary zones, and will be active in defence of a territory and will do so vigorously by running afteran intruderduring which loud calls, grunts, pecking (striking) and kicking displays occur, sometimes causing injury. The investigation commenced during the early stages of the breeding period and it is likely that some of the territory defence is associated with the breeding season.
Foraging efficiency comparison
Foraging comprises of pecking vigorously into the soil substrate (with bill slightly open which then grasps the seed), where by acquiring fine herbage, seed and a few invertebrates, often exceeding 100 pecks perminute (Figure 4). These feeding items are widely and more or less evenly distributed and the hens move steadily, grazing over most of their territory during the day (Ridpath 1971), interrupted by rising of the head quickly to determine that it is safe to continue, this activity usually lasting only one or two second before vigorous pecking resumes.
Foraging efficiency differed between the two habitats, individuals in the agricultural zones spent more time in a vigilant state with each alert pose lasting longerin duration than that of individuals in the estuary habitat, in some instances up to ten seconds. The vigilant state of individuals in the estuary habitat whilst more frequent, was short lived in most instances lasting one or two seconds, allowing for more foraging efficiency overall (Figure 4). Due to varied weather conditions during August, native hens in open more vulnerable agricultural zones, were not always foraging early morning or late afternoon as was predictable in the estuary habitat, therefore inspections of the site at random during daylight hours was required to attain balanced time allocation of sampling per habitat.
Tail Flick behaviour
Tails flicking can occur simultaneously with the head being erect, though in some instances would occur during pecking. Alarm responses of native hens are diverse, to include a slightly raised head whilst observing a predator, will tilt the head slightly depending on where the predatoris, for example airborneoroffset of view, at this point the tail flick may develop with head stretched and elevated, still watching the predator, whilst the tail is erect and flicking sporadically in a vertical position, each tail flick is fast, usually less than a second. Tail flicking was rapid during the alert pose in all native hens sampled in the agricultural zone. In some instances tail flicking did not occur at all in individuals within the estuary habitat, on occasions would occur during pecking activity. A dampened alarm call may be heard in response to a ground predator, this soft low call can often be hard to detect though appeared distinctive to the native hens family group.
A wing flick can occur and is more so associated with the presence of human, dog and wedge-tailed eagle Aquila audax, all deemed more dangerous to adult native hens (Ridpath 1971). The wing flick action is also very rapid and appears to be similar to that of a comparable species that do fly, and usually in response to aerial predators. Goshawks are frequently seen in the vicinity of Skeleton Creek study site, togetherwith the return of the migrating Swamp harrier. A sharp alarm call is used to warn others of imminent dangerand can be heard at greaterdistances than the lower deep grunt call.
.
Acknowledgement
Thanks to local Naturalist Peter Tonelli for his knowledge insight into Tasmanian endemic avifauna species particularly local to the North-west region, and for the image in Figure 1.
References
Goldizen, AW, Putland, DA & Robertson, KA 2002, Dispersal strategies in Tasmanian native hens
(Gallinula mortierii) Behavioural Ecology, Vol. 13, No 3: 328-356
Maynard Smith, J & Ridpath MG, Wife Sharing in the Tasmanian native Hen, Tribonyx mortierii: A Case of Kin Selection? The American Naturalist Vol. 106, No. 950 (Jul. – Aug., 1972), pp. 447-45
Putland, DA & Goldizen, AW 2001, Family dynasties in the Tasmanian nativehen (Gallinula mortierii). Behav Ecol Sociobiol 51:25-32.
Ridpath , MG 1964. The Tasmanian native hen, Tribonyx mortierii, pp. 346-350. Australian Natural History, Vol. xiv, No 11. CSIRO Hobart Tas.
Ridpath, MG 1972a. The Tasmanian native hen, Tribonyx mortierii. I. Paterns in behaviour. CSIRO Wildl Res 17:1-51.
Ridpath, MG 1972b. The Tasmanian native hen, Tribonyx mortierii.II. The individual, the group, the population. CSIRO Wildl Res 17:53-90.
Alison,
I really don’t know what you did, your methods and results are so unrelated to your vague aims. Your methods are not up to scratch. Your use of the literature is almost non-existent.
I would like you to go back to the start, gather a whole lot of relevant literature – nothing from a date that starts with a ‘19 ‘. Not just about these hens, but about rails in general, about bird foraging behavior in general. About the two habitats you chose
Make the reader understand why it is important that you did the research.
State the aims of your research CLEARLY.
Describe how you chose and measured the behavioural variables required to test the questions associated with those aims
Describe how you measured the variables.
Describe how you tested them
State the results to your test.
Discuss the results.
Wayne R
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In the estuary the mean pecking rate of Tasmanian native hens was 101.9 pecks per minute (SE = 0.82), with an average of 1.35 tail flicks per minute (SE = 0.25). In the agricultural system the bird averaged 73.5 pecks per minute (SE = 0.43) and 1.9 tail flicks per minute (SE = 0.86.).
Nevertheless, it is unusual to write up the averages without including the results of the tests?
AND IF THE DATA ARE PAIRED as you suggest – then the individual averages are meaningless. It’s the mean of the paired differences that is of interest….
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