“It does not matter how abundant nectar may be in any one place, the numbers of nectar-feeders will be determined by the amount of nectar in [their] least abundant
habitat.” (Recher, 1999)
“The abundance and kinds of food resources in eucalypt forest not only influence where birds forage, but also determine overall community structure and richness” (Recher et
al., 1991).
INTRODUCTION
The Nectarivores are a conspicuous and abundant component of the karri forest avifauna, comprising 18% of the species and nearly 40% of individuals (Wardell- Johnson and Williams, 2000). This is not surprising because carbohydrate-dependent species are typically the most abundant birds in eucalypt ecosystems (Recher et al., 1991). The abundance of these birds and their potential role as pollinators are important reasons to determine their responses to forest management practices, both as a guild and as individual species.
The Honeyeaters (Meliphagidae) are the major nectar feeders in the Australian biota - a large family (23 genera and 71 species in Australia) of nectarivores endemic to Australia, New Guinea, New Zealand and the Pacific Islands (Keast, 1985; Sibley and Ahlquist, 1990). They have long, protrusible brush tongues specialised for nectar feeding (Sibley and Ahlquist, 1990 p612). Some other taxa occurring in Australia also
Chapter 4 : Nectarivores
In the karri forest of Western Australia, the nectarivore guild is made up of one member of the Psittacidae family (the Purple-crowned Lorikeet, which feeds on eucalypt pollen and nectar (Churchill and Christensen, 1970; Christensen, 1971; Hopper, 1980)), and eight Meliphagidae species. Four Meliphagids are common species (White-naped Honeyeater, New Holland Honeyeater, Red Wattlebird and Little Wattlebird) while four are uncommon (Brown-honeyeater, Western Spinebill, Singing Honeyeater, Tawny-crowned Honeyeater). The Purple-crowned Lorikeet, White-naped Honeyeater and New Holland Honeyeater are the three most abundant species in karri forest (Wardell-Johnson and Williams, 2000; Williams et al., 2001).
Nectarivores and edges
Most studies on edges have been conducted in temperate or boreal America and Europe (e.g., Table 1.1) where there are relatively few nectarivores. And very few studies on Edge Effects have tested the distribution of bird foraging guilds across edges (e.g., Lopez de Casenave et al., 1998 (but did not include Nectarivores as a guild); Restrepo and Gomez, 1998 (understorey birds only); Dale et al., 2000). For these two reasons, the edge responses of nectarivores are particularly poorly known. It appears from the data of existing studies that nectarivores outside Australia may prefer the young side of edges (De Graaf, 1992; Kruger and Lawes, 1997; Restrepo and Gomez, 1998; Dale et al., 2000).
Chapter 4 : Nectarivores
edges. None of the species that responded to edges in jarrah forest studies were nectarivores. Wardell-Johnson and Williams (2000) in karri forest showed that the Purple-crowned Lorikeet, the New Holland Honeyeater and the White-naped Honeyeater had significant differences in abundance across Establishment edges and all were least abundant 100-300m into young regrowth and most abundant 100-300m into mature forest. The White-naped Honeyeater also declined in logged jarrah forest (Craig, 1999), and was lower in abundance in logged forest in NSW and Victoria (Loyn, 1980; Kavanagh et al., 1985; Loyn, 1985a). The Red Wattlebird was less common in logged forest in Victoria (Loyn, 1985a) while the New Holland Honeyeater was more abundant in regenerating forest in southern NSW (Smith, 1985a,b) but was only observed in old-growth forest and not in regrowth in Tasmania (Hingston, 2000).
Nectarinia olivacea was one of the eight most common species in Dale et al.’s (2000) study on avian guilds and edges in Uganda, but only two individuals were recorded for the other two species in the nectarivore guild. This meant that a single species’ response determined the overall guild effect. This example demonstrates the importance of examining individual species responses to edge before generalising at the level of guild. A single species could dominate the response pattern for the guild, or the species within the guild could respond quite differently to karri forest edges.
The aims of this chapter are:
1) To examine and compare the response to clear-fell karri forest edges of the nectarivore guild as a whole with each of the five common nectarivore species. Is it possible to generalise for the nectarivore species using a whole guild response?
Chapter 4 : Nectarivores
2) To determine if the distribution of the nectarivore species varies according to the factors of Time, Edge, Age, or forest Area, or to interactions involving them
3) To compare the behaviour of the Nectarivore species across edges by examining their use of height strata, foraging substrate and foraging technique. Their behavioral traits or behavioural flexibility may influence their edge response.
METHODS
This study follows the foraging guilds designated by Wardell-Johnson and Williams (2000). The Silvereye (Zosterops lateralis) feeds on nectar as well as fruit, however, I have included it with the Granivore/Frugivore guild for this study, following Wardell- Johnson and Williams (2000). Details of field site information and the bird census methods used for data collection for this chapter are presented in Chapter 2 together with details of statistical analysis.
Analysis of distribution data
Data for the five common Nectarivore species only (those with more than 100 observations in the first year) were analysed together by Repeated Measures ANOVA
Chapter 4 : Nectarivores
The overall design is incomplete (Chapter 2). It was my original intention to sample all census points for eight seasons, but this was not possible because of logging and other disruptions to the study sites (scrub-rolling, road-building, etc) after four seasons. Thus two related datasets are considered here: firstly, a one year study allowing assessment of site differences as well as influences of edge and season, and secondly a two year study at one amalgamated to determine seasonal effects over a two-year time scale (see Chapter 2 for a detailed description of the design).
The critical terms in the analyses are the interactions, especially those involving both the factors Edge and Age, because numbers were not standardised between treatments at the beginning of the experiment. The factor Area is of interest in relation to the factors Edge and Age – to determine if patterns of nectarivore distribution across Edge and Age are consistent between forest blocks. Similarly, the factor Time is of interest to determine if patterns of nectarivore distribution across Edge and Age are consistent with Time.
Analysis of behavioural, bird-banding and rare species data
Foraging and behavioural observations were made during the census, using the methods and categories described in Chapter 2. Six behavioural parameters, each containing a variable number of categories were opportunistically recorded for each species. Not all of these parameters were recorded in any one bird observation, thus total numbers of observations for each species vary for each parameter.
Chapter 4 : Nectarivores
Establishment, Juvenile, Mature), Edge (Distance across the Edge - 120m and 60m into regrowth, Edge, and 60m into Mature forest) and Habitat, and number of captures as the dependent variable. In this case, Habitat was divided into four categories: Establishment regrowth, Juvenile regrowth, Edge, and Mature forest. The distributions of two of the uncommon nectarivore species (Brown Honeyeater and Western Spinebill) were tested using a permutation method (Good, 1994; Driscoll, in press; refer to Chapter 2 for details) to determine if sightings were associated with any of three habitat categories – Mature forest, Edge or Regrowth.
RESULTS
Summary data for Nectarivores in Year 1 and over 2-years are shown in Appendix Tables 9 and 10.
Year 1 - Analysis of the first year data showed significant interactions between the factors Area*Age*Edge, Age*Edge*Species, Time*Edge*Species and Time*Area*Age*Species (Table 4.1). For the interaction of Area*Age*Edge (Figure 4.1), all three forest areas showed the same general pattern of significantly higher abundance in mature forest than 120m or 60m into either Establishment or Juvenile regrowth. In all forest areas (Gray, Jane and Sutton), the Juvenile edge had significantly fewer nectarivores than the mature forest treatment within that area. In two of the three areas, Establishment edges were no different to mature forest, but in Sutton they were
Chapter 4 : Nectarivores
Juvenile regrowth. Although each species demonstrated a similar pattern of lowest abundance in regrowth, aspects of the pattern were more pronounced in some species than in others. The Purple-crowned Lorikeet, the White-naped Honeyeater, the New Holland Honeyeater and the Little Wattlebird all had lower abundance at Juvenile edges than in mature forest, while the White-naped Honeyeater also had lower abundance at Establishment edges. There was no difference in abundance between any of the census points 60m into mature forest, regardless of transect age, for any of the five species. In the first year of censusing, four of the five nectarivore species avoided Establishment and Juvenile regrowth, and Juvenile edges, while the White-naped Honeyeater also avoided Establishment edges. The Red Wattlebird was less abundant in Establishment and Juvenile regrowth, but did not avoid edges.
The interaction of Time*Edge*Species (Figure 4.3) revealed differences in nectarivore species’ edge responses between seasons. The New Holland Honeyeater had a consistent edge response regardless of season, with significantly lower numbers 120 and 60m into regrowth, and higher numbers at the edge and 60m into mature forest. The Purple-crowned Lorikeet had a stronger edge response in spring, the White-naped Honeyeater had a stronger response in autumn and winter, and the Little Wattlebird in spring and autumn. Each nectarivore species was at peak abundance at a different time of the year. This temporal response can best be seen in the interaction between Time*Area*Age*Species (Figure 4.4). Each species has peaks and troughs in abundance in different seasons and different forest areas. However, mature forest consistently has higher numbers of each nectarivore species than the other age treatments.
Chapter 4 : Nectarivores
Two Years - When nectarivore abundance was analysed for two years (eight seasons) in one forest area, the interactions between Age*Edge, Time*Age*Species and Time*Edge*Species were significant (Table 4.2). The interaction of Age*Edge (Figure 4.5) showed that for all time periods, mature forest was higher in nectarivore abundance than either Establishment or Juvenile regrowth, and that Establishment and Juvenile regrowth sites were different to each other. Establishment edges were lower in abundance than mature forest, and 60m into mature forest from Establishment regrowth, there was still lower nectarivore abundance, whereas Juvenile edges and 60m into mature forest from Juvenile regrowth were not significantly lower in nectarivore abundance than mature forest.
This at first seems to contradict the results from the first year’s sampling where the interaction for Age*Edge*Species (Figure 4.2) showed that four of the five species had significantly lower abundance at Juvenile edges when compared to Establishment edges or mature forest. This result for the 2-year analysis could be caused by the amalgamation of Jane and Sutton forest blocks into one complete set of replicates for the second year of sampling (necessary because of non-demonic influences, refer to Chapter 2). The Establishment transects sampled in the second year were all from Sutton block. The Juvenile regrowth transects sampled in the second year were all from Jane block, while the mature forest transects were from both forest areas. The interaction between Area*Age*Edge for the first year showed that the Establishment edges at Sutton forest block were significantly lower than for the other forest areas in
Chapter 4 : Nectarivores
birds at the Establishment edge. Because Purple-crowned lorikeets were one of the more abundant nectarivore species, low numbers could have skewed the mean.
The interaction of Time*Age*Species over two years showed that each species had peaks and troughs in abundance at different times of the year. Because the transects sampled for two years were amalgamations of Jane and Sutton forest blocks (see above and chapter 2 for site and experimental design details), the patterns in Establishment regrowth in the first of the two years (Figure 4.6) can be compared directly to Establishment regrowth for Sutton forest block in Figure 4.4. Similarly, Juvenile regrowth in the first of the two years (Figure 4.6) can be compared directly to Juvenile regrowth for Jane block in Figure 4.4. Each species tended to have highest abundance in mature forest over the two years, followed by Juvenile and Establishment regrowth, although these differences were not significant for all seasons or for all species. Interestingly, while the Little Wattlebird was most abundant in autumn in the first year, in the second year it was most abundant in summer, as were the Purple-crowned lorikeet and Red Wattlebird. In the second year, all species except the New Holland Honeyeater were more abundant than in the first.
The interaction of Time*Edge*Species (Figure 4.7) revealed that all species had higher abundance 60m into mature forest and at the edge than in either Establishment or Juvenile regrowth, although this trend was not always statistically significant.
The results from both the first year analysis - showing the interactions between Edge and Age in four seasons and three forest areas - and the analysis of data from two years (eight seasons) in one forest area demonstrate that the abundance of nectarivores in karri forest fluctuates greatly in both time and space. However, both analyses showed that the interaction of Edge*Age remains consistent throughout both time and
Chapter 4 : Nectarivores
data. This interaction showed that four of the five nectarivore species avoided Juvenile edges, and that one of these four also avoided Establishment edges. For the smaller 2- year data set this interaction was not significant.
Behavioural data.
Height Frequency - Tables 4.3 and 4.4 summarise the frequency of heights used by the New Holland Honeyeater and the White-naped Honeyeater, the two most abundant Nectarivores, in different habitats and seasons. Seasonal and habitat data could not be analysed with Log Linear Analysis for the other three species because they had few observations in some seasons or habitats (Purple-crowned Lorikeet) or too few observations overall (Red and Little Wattlebirds). The Log-linear analysis revealed a 3- way interaction between the factors height, habitat and season (Table 4.4). The Purple- crowned Lorikeet was commonly observed quite high in the profile, peaking at 31-40m. The Red and Little Wattlebirds used a variety of heights, although the Little Wattlebird had a peak at 2-5m, and the Red Wattlebird a peak at 21-30m. The New Holland Honeyeater changed its height between seasons (Table 4.4), predominantly using lower strata in spring in both years, and summer in the second year, but higher strata in autumn in both years and winter in the second year. In summer and winter in the first year, the New Holland Honeyeater used both high and low strata. The White-naped Honeyeater predominately used low strata in spring in both years (Table 4.4), and generally used higher strata in summer, autumn and winter in both years, although in
Chapter 4 : Nectarivores
The New Holland Honeyeater and White-naped Honeyeaters also showed differences in their height profiles with habitat (Table 4.3). Log-Linear analysis of these data revealed a 3-way interaction between the factors height, habitat and species. Both species used a lower profile in the Establishment regrowth and the Juvenile regrowth than in Edge habitat or Mature forest. The White-naped Honeyeater was not observed higher than 10m in regrowth, while the New Holland Honeyeater was not observed higher than 20m in regrowth.
Activity and Substrate - The Purple-crowned Lorikeet was mostly observed singing or flying (Table 4.7). It used small twigs and flowers as its main activity sites (Table 4.5), and was mainly found in the outer foliage of the canopy (Table 4.6). It was the least diverse of the nectarivores in its observed activity sites and use of vegetation structure. The Purple-crowned Lorikeet fed mainly on flowers with a smaller percentage of foraging hawking or flitting for invertebrates (Table 4.8).
The White-naped Honeyeater was most frequently observed foraging (Table 4.7). Like all the nectarivore species, it predominately used small twigs and branches as its main activity site, followed by leaves and foliage, and air (Table 4.5). The vegetation strata used were mainly inner and outer canopy foliage, but also trunks and inner branches, scrub leaes and above the scrub (Table 4.6). The White-naped Honeyeater foraged by picking and gleaning, with a small proportion of probing/tearing and flower pecking (Table 4.8).
The New Holland Honeyeater Honeyeater was observed flying, singing, in social interactions, foraging and territory defense (Table 4.7). It also mainly used small twigs and foliage (Table 4.5), and was found in scrub on leaves and live sticks, above the scrub, and in inner and outer canopy foliage (Table 4.6). The New Holland
Chapter 4 : Nectarivores
Honeyeater was mainly observed foraging on flowers and nearly as frequently, picking and gleaning (Table 4.8).
The Little Wattlebird was most often observed singing, then flying, in social interactions and foraging (Table 4.7). It again mainly used twigs and small branches, then air, and bigger branches (Table 4.5). It had no pronounced peak in any vegetation stratum, but used inner and outer canopy foliage, above scrub, and trunks and inner branches (Table 4.6). The Little Wattlebird foraged mainly by picking/gleaning, probing/tearing and flower pecking (Table 4.8). The Red Wattlebird was observed predominantly flying, then foraging, singing and resting (Table 4.7). It used twigs and small branches, air, and flowers (Table 4.5). It was found predominantly on outer canopy foliage, followed by inner canopy foliage and trunks/inner branches (Table 4.6). The Red Wattlebird foraged mainly by flower pecking, and probing/tearing (Table 4.8).
Vegetation - The Purple-crowned lorikeet was the most specific in its vegetation association, and was observed almost exclusively on Karri, with a small proportion of marri (Figure 4.8). The New Holland Honeyeater, in contrast, used the most diverse range of plant species (Figure 4.8). The proportion of karri used was over 40% for each of the five nectarivore species (Figure 4.8). Nectar producing plants include the trees karri, marri, and jarrah, and the understorey plants, Choralaena quercifolium, and kangaroo paw (Anigozanthus flavidus). The latter occurred almost exclusively in Establishment regrowth coupes where there was more sun, and was used as a seasonal nectar source by New Holland Honeyeaters in that habitat. Choralaena quercifolium
Chapter 4 : Nectarivores
Bird-banding data and uncommon species.
One hundred and ninety one New Holland Honeyeaters, 37 White-naped Honeyeaters, two Red Wattlebirds and one Little Wattlebird were banded during this study. Five New Holland Honeyeaters (2.6%) and one White-naped Honeyeater were recaptured (2.7%). Of the New Holland Honeyeaters recaptured, two were recaptured at the same net, one at an adjacent net 60m away. All three recaptures were on mature forest transects. The remaining two birds were recaptured at different sites some distance apart, one moving from a juvenile edge to a mature forest transect, and the other from a mature forest transect to a net 60m into Establishment regrowth. The White-naped Honeyeater was recaptured at the same net site a year after banding.
New Holland Honeyeater capture data showed a significant interaction between the factors Age*Edge (Table 4.9, Figure 4.9). New Holland Honeyeaters were captured significantly more frequently in mature forest transects than in regrowth transects and in Mature forest and Edge habitats than Establishment or Juvenile regrowth habitats. White-naped Honeyeaters (Table 4.9, Figure 4.9) showed no significant differences in the number of captures with transect age, distance across the edge, Habitat or the