Translocation of Threatened New Zealand Falcons to Vineyards Increases Nest Attendance, Brooding and Feeding Rates

Anthropogenic landscapes can be rich in resources, and may in some cases provide potential habitat for species whose natural habitat has declined. We used remote videography to assess whether reintroducing individuals of the threatened New Zealand falcon Falco novaeseelandiae into a highly modified agricultural habitat affected the feeding rates of breeding falcons or related breeding behavior such as nest attendance and brooding rates. Over 2,800 recording hours of footage were used to compare the behavior of falcons living in six natural nests (in unmanaged, hilly terrain between 4 km and 20 km from the nearest vineyard), with that of four breeding falcon pairs that had been transported into vineyards and nested within 500 m of the nearest vineyard. Falcons in vineyard nests had higher feeding rates, higher nest attendance, and higher brooding rates. As chick age increased, parents in vineyard nests fed chicks a greater amount of total prey and larger prey items on average than did parents in hill nests. Parents with larger broods brought in larger prey items and a greater total sum of prey biomass. Nevertheless, chicks in nests containing siblings received less daily biomass per individual than single chicks. Some of these results can be attributed to the supplementary feeding of falcons in vineyards. However, even after removing supplementary food from our analysis, falcons in vineyards still fed larger prey items to chicks than did parents in hill nests, suggesting that the anthropogenic habitat may be a viable source of quality food. Although agricultural regions globally are rarely associated with raptor conservation, these results suggest that translocating New Zealand falcons into vineyards has potential for the conservation of this species

Evidence synthesis as the basis for decision analysis: a method of selecting the best agricultural practices for multiple ecosystem services

Agricultural management practices have impacts not only on crops and livestock, but also on soil, water, wildlife, and ecosystem services. Agricultural research provides evidence about these impacts, but it is unclear how this evidence should be used to make decisions. Two methods are widely used in decision making: evidence synthesis and decision analysis. However, a system of evidence-based decision making that integrates these two methods has not yet been established. Moreover, the standard methods of evidence synthesis have a narrow focus (e.g., the effects of one management practice), but the standard methods of decision analysis have a wide focus (e.g., the comparative effectiveness of multiple management practices). Thus, there is a mismatch between the outputs from evidence synthesis and the inputs that are needed for decision analysis. We show how evidence for a wide range of agricultural practices can be reviewed and summarized simultaneously (“subject-wide evidence synthesis”), and how this evidence can be assessed by experts and used for decision making (“multiple-criteria decision analysis”). We show how these methods could be used by The Nature Conservancy (TNC) in California to select the best management practices for multiple ecosystem services in Mediterranean-type farmland and rangeland, based on a subject-wide evidence synthesis that was published by Conservation Evidence (www.conservationevidence.com). This method of “evidence-based decision analysis” could be used at different scales, from the local scale (farmers deciding which practices to adopt) to the national or international scale (policy makers deciding which practices to support through agricultural subsidies or other payments for ecosystem services). We discuss the strengths and weaknesses of this method, and we suggest some general principles for improving evidence synthesis as the basis for multi-criteria decision analysis

Sunflower damage and bird diversity data 2014-2015

The “sunflower damage and bird data” provides a summarized dataset on the amount of bird and insect damage to commercial sunflower seed crops in 30 fields in Yolo County, California. Data was collected over 2 years and was spread geographically across the sunflower regions of the county to incorporate fields that were varying distances from remnant natural habitat in the county. Fields had either bare/weedy margins (the linear areas along the edges of fields that are not planted with crops), or had woody vegetation along margins (trellises, riparian corridors, or hedgerows). Sunflower damage was measured by randomly sampling from 10 plants at distances from 0-200m from the field margin and estimating the proportion of all seeds removed by birds or damaged by sunflower head moth. Avian diversity metrics were calculated using data from two site visits in the summer and two in the fall- each visit included a 200m one-sided line transect to count birds utilizing field margin habitat, and a 10- minute point count to count birds utilizing field interiors. Data includes the mean proportion of 10 sampled sunflowers at each distance from the field edge that was damaged by insects or birds. Information on the field margin habitat complexity, the proportion of natural habitat within varying distance bands (50m-800m) from the center of the field margin, and numerous avian diversity and abundance metrics collected in both summer and fall are also included. The exact locations of fields and names of sites are not included to protect farmer privacy. A metadata tab is included in the spreadsheet to provide information about each column of data. Data is presented as an excel file including two tabs- one with the data, and one containing metadata explaining each column. Keywords: agroecology, Crop damage, ecosystem services, farm, Hedgerow, Integrated Pest Management, Pest Control, landscape, ornitholog

Insect Pest Control and Bird Damage as a Function of Distance from Riparian Habitat in a California Vineyard

Farmers have few tools with which to objectively assess the true impact of avian species on crop production, partly because ecologists and conservationists have been slow to quantify the role of birds within agricultural settings. At an annual value of over $5.5 billion dollars, vineyards are the third-most-valuable agricultural crop produced in California. Vineyard area has rapidly expanded in California and now covers at least 820,000 acres. Encouraging growers to retain existing natural habitat around vineyards or install new habitat, such as hedgerows, is likely to have positive effects on biodiversity. However, viticulturists are often wary of actions that could increase wildlife numbers on their land, particularly birds, since they are considered one of the most damaging pests to vineyards worldwide. In California, over 67% of vineyard acres have some degree of bird damage, with estimates ranging from between 5.4% and 16.1% of crops damaged. Conversely, birds may provide vineyards with valuable pest control services by consuming insects in high numbers in the spring and summer. Quantifying these costs (bird damage) and benefits (insect pest control) for vineyards from birds as they relate to natural habitat is an essential step in understanding the net value of nature in vineyard ecosystems. In July 2015, I used a sentinel prey experiment in a California vineyard to measure the relationship between insect pest-control, bird damage, and distance from a riparian corridor. I found that over 40% of sentinel prey were consumed at the edge of the vineyard, and that birds damaged 12% of grapes. Depredation of sentinel prey and grape damage dropped at a similar rate with increasing distance from riparian habitat. These results suggest that birds may remove insect pests at a rate that could offset the damage caused by avian foraging once grapes are ripe, but further studies are needed to confirm this

Gopherbusters? A Review of the Candidacy of Barn Owls as the Ultimate Natural Pest Control Option

While many raptor species consume rodent pests, the behaviors and habits of barn owls make them particularly suitable candidates for consideration as a viable pest control strategy. As a cavity-nesting species, barn owls will readily nest in man-made structures including nest boxes. Barn owls are also less territorial than many other raptor species and will tolerate other pairs nesting nearby if prey is abundant. Barn owls preferentially consume rodents including voles (Microtus spp.) and pocket gophers (Thomomys spp.) in habitats where they occur, but will also switch to more abundant prey so they may be able to sustain populations even if preferred prey numbers fall. These life-history traits allow for people to inflate barn owl populations in target areas, and this has been a factor in the widespread popularity of encouraging barn owls to nest in agricultural areas to provide natural pest control of small nocturnal vertebrate pests. However, the ability of barn owls to control rodent pests has only been formally tested in Malaysian rice and palm oil agriculture, and whether barn owls are capable of controlling rodent pests to economically acceptable levels in areas such as California is as yet unknown. We extracted and combined data from field studies of barn owl nesting behavior and diet in California vineyards to predict that annually, a pair of nesting barn owls and their progeny will consume 97.85 kg of prey. We predicted that an average barn owl nest in a California vineyard will therefore consume 843 pocket gophers, 578 voles, and 1,540 other prey items, most of which are mice. At these values, a barn owl population density of one nest/10 ha may be able to offset the annual productivity of an average population of pocket gophers, but even the highest barn owl densities of one nest/2 ha would be unable to control pocket gopher populations at maximum densities and reproductive rates. While valuable for making initial predictions of the ability of owls to control small rodent pests, our prediction methods are crude, and accurately assessing the capability of barn owls to control rodent pests will require more field data and more sophisticated modeling techniques

Gopherbusters? A Review of the Candidacy of Barn Owls as the Ultimate Natural Pest Control Option

While many raptor species consume rodent pests, the behaviors and habits of barn owls make them particularly suitable candidates for consideration as a viable pest control strategy. As a cavity-nesting species, barn owls will readily nest in man-made structures including nest boxes. Barn owls are also less territorial than many other raptor species and will tolerate other pairs nesting nearby if prey is abundant. Barn owls preferentially consume rodents including voles (Microtus spp.) and pocket gophers (Thomomys spp.) in habitats where they occur, but will also switch to more abundant prey so they may be able to sustain populations even if preferred prey numbers fall. These life-history traits allow for people to inflate barn owl populations in target areas, and this has been a factor in the widespread popularity of encouraging barn owls to nest in agricultural areas to provide natural pest control of small nocturnal vertebrate pests. However, the ability of barn owls to control rodent pests has only been formally tested in Malaysian rice and palm oil agriculture, and whether barn owls are capable of controlling rodent pests to economically acceptable levels in areas such as California is as yet unknown. We extracted and combined data from field studies of barn owl nesting behavior and diet in California vineyards to predict that annually, a pair of nesting barn owls and their progeny will consume 97.85 kg of prey. We predicted that an average barn owl nest in a California vineyard will therefore consume 843 pocket gophers, 578 voles, and 1,540 other prey items, most of which are mice. At these values, a barn owl population density of one nest/10 ha may be able to offset the annual productivity of an average population of pocket gophers, but even the highest barn owl densities of one nest/2 ha would be unable to control pocket gopher populations at maximum densities and reproductive rates. While valuable for making initial predictions of the ability of owls to control small rodent pests, our prediction methods are crude, and accurately assessing the capability of barn owls to control rodent pests will require more field data and more sophisticated modeling techniques

New Zealand Falcon nests suffer lower predation in agricultural habitat than in natural habitat

Introduced mammalian predators have been implicated in the majority of avian extinctions on oceanic islands around the globe. Nowhere is this more apparent than in the decimated New Zealand avifauna, where introduced predators remain the primary threat to virtually all surviving endemic species, including the threatened New Zealand Falcon 'Falco novaeseelandiae'. We used remote videography at falcon nests and conducted an artificial nest experiment to compare the rates of predation and responsible predators of falcons nesting in hills against those nesting in nearby commercial vineyards. Overall, 63% of artificial nests in the hills were predated, compared with 38% in vineyards. Further, artificial eggs were predated faster in the hills than those placed in vineyards. Video footage revealed that the suite of predators visiting real falcon nests was similar to those identified attacking artificial nests. However, predators differed across habitats, with nests in vineyards being predated mainly by hedgehogs 'Erinaceus europaeus' and Australasian Harriers 'Circus approximans', whereas nests in the hill environments were mainly attacked by stoats 'Mustela erminea'. These results demonstrate the important implications of habitat type on predation pressure associated with introduced predators. These may well prove a fruitful avenue of management if breeding can be fostered in safer areas, as in the case of this threatened falcon

Proportion of the day that both adult falcons were in attendance at the nest as chick age increased in vineyard (dotted lines) and hill (solid lines) nests.

<p>Thin grey lines show the raw data for both parents combined, with +SEM for vineyard nests and the data mean –SEM for hill nests. Thick lines show the fitted values from a GLMM including significant second and third order polynomial terms for female falcons (black lines) and from a GLMM including significant second order polynomial terms for male falcons (dark grey lines).</p

The total biomass of prey brought into nests in vineyards and hills.

<p><b>A</b> The minimum, lower quartile, median, upper quartile, and maximum observations for vineyard nests with supplementary food items excluded (V), for vineyard nests including supplementary food items (VS) and for hill nests (H). <b>B</b> The fitted model estimates from a GLMM with a significant second order polynomial fitted for chick age, including supplementary food for vineyard nests (VS) and excluding supplementary food (V) and for hill nests (H). Model estimates indicated that as chick age increased falcons in vineyard nests brought in more total prey each day than did falcons in hill nests (<i>P</i><0.001).</p