Are There Snags in the System? Comparing Cavity Use among Nesting Birds in “Snagrich” (original) (raw)
Related papers
2002
We compared the density of snags, snags with cavities, and cavity-nesting bird use at two sites in northern California: Blacks Mountain Experimental Forest, a site with large trees and large snags because of protection from logging, contrasted with the Goosenest Adaptive Management Area, where a century of logging left this forest with few large trees and snags. Indeed, there was a threefold difference between sites in total snags, and a fifteenfold difference in cavity-nesting bird use. However, we feel finding a "snags per acre" prescription is inadequate, as tree size, rate of snag generation, and mode of tree death have been disrupted this past century. We argue that understanding the interactions between fire, bark beetles, woodpecker foraging and excavating, sapwood decay organisms, snag "demography," and cavity-nesting species ecological requirements apart from simply cavities are required in place of simply counting snags in landscapes.
… , William F., Jr.; Shea, Patrick J. …, 1999
We compared the density of snags, snags with cavities, and cavity-nesting bird use at two sites in northern California: Blacks Mountain Experimental Forest, a site with large trees and large snags because of protection from logging, contrasted with the Goosenest Adaptive Management Area, where a century of logging left this forest with few large trees and snags. Indeed, there was a threefold difference between sites in total snags, and a fifteenfold difference in cavity-nesting bird use. However, we feel finding a "snags per acre" prescription is inadequate, as tree size, rate of snag generation, and mode of tree death have been disrupted this past century. We argue that understanding the interactions between fire, bark beetles, woodpecker foraging and excavating, sapwood decay organisms, snag "demography," and cavity-nesting species ecological requirements apart from simply cavities are required in place of simply counting snags in landscapes.
Snags and Cavity-Nesting Birds within Intensively Managed Pine Stands in Eastern North Carolina, USA
2011
Although snags are often considered to be a limiting factor for cavity-nesting birds within intensively managed pine (Pinus spp.) stands, there is little information regarding occurrences of snags and cavity-nesting birds for such stands in the southeastern United States. Therefore, during 2002-2003, we measured characteristics of individual snags (n ϭ 1,218) and quantified the relative abundance of cavity-nesting birds (n ϭ 204 observations; nine species) in 35 forest stands representing seven thinning classes (prior to thinning, three age classes following a first commercial thinning, and three age classes following a second commercial thinning entry) in intensively managed pine stands in eastern North Carolina. Snag populations were dynamic, with 649 snags falling and 75 new snags recruited between years. Stands in later thinning classes tended to have snags with larger diameters, less bark, and fewer limbs, and they were taller and more decayed (P Ͻ 0.05). Our data suggest that neither density of snags (P ϭ 0.31) nor relative abundance of cavity-nesting birds (P ϭ 0.25) differed strongly among thinning classes. Without active management, low recruitment coupled with the high loss rates that we observed could lead to low snag densities in older managed stands. Therefore, we suggest that forest managers consider retaining large-diameter dead or live trees as reserve trees through multiple rotations to increase or maintain snags in managed stands.
Use of Artificially Created Douglas-Fir Snags by Cavity-Nesting Birds
Western Journal of Applied Forestry, 1997
In western Oregon, we created snags by sawing tops off live Douglas-fir (Pseudotsuga menziesii) (n = 821) trees and monitored their condition and use by cavity-nesting birds. We created snags in three silvicultural treatments: modified clearcut stands, two-story stands, and small-patch group-selection stands. We used two snag patterns: clumped and scattered. Created snags averaged 3.8/ha in density, 17 m in height, and 75 cm in diameter. Chainsaw-topped snags were used by cavity nesters within 5 yr of creation. Abundance of excavated cavities increased in all silvicultural treatments (P = 0.0001) and was higher in twostory and clearcut stands than in small-patch stands (P _<0.0004). We did not, however,find that snag pattern (clumped v. scattered) affected use by cavity-nesting birds based on abundance of excavated cavities (P > 0.6). We observed excavated cavities in five hardwood species indicating that hardwoods represented an important resource for cavity-nesting birds. Creating conifer snags by topping and retaining hardwoods may retain or increase populations of cavity nesters in areas with low natural snag density. West. J. Appl. For. 12(3):93-97. Dead standing trees (snags) are a natural component of forests. They are created by wind (stem breakage), fire, lightning, insects, drought, flooding, disease, and the natural death and decay of a tree (Bull 1986, Adkisson 1988, Morrison and Raphael 1993). Snags are an essential habitat component for many species of primary and secondary cavity-nesting birds (Thomas et al. 1979, Brown 1985). Density of cavity-nesting birds is associated with snag density (Thomas et al. 1979, Bull and Meslow 1977,
Forest Ecology and Management, 2004
Snags provide an important resource for a rich assemblage of cavity-nesting birds in the southwestern United States. To expand our knowledge of snag use by cavity-nesting birds in this region, we documented characteristics of snags with and without excavated cavities in mixed-conifer and ponderosa pine (Pinus ponderosa Dougl. ex Laws) forest in north-central Arizona. Snags were sampled in 113 square plots (1 ha each) randomly located within a study area covering approximately 73,000 ha across two National Forests. Density of snags was three times greater in mixed-conifer forest (n ¼ 53 plots) than in ponderosa pine forest (n ¼ 60 plots), but density of snags containing cavities and overall cavity density did not differ between forest types. In both forest types, snags containing cavities were larger in diameter and retained less bark cover than snags without cavities. Most cavities were in ponderosa pine and Gambel oak (Quercus gambelii Nutt.) snags, and most were in snags in advanced decay classes with broken tops. Our results are largely consistent with previous results from ponderosa pine forest, but differ from previous studies that documented heavy use of quaking aspen (Populus tremuloides Michaux) by cavity nesters in mixed-conifer forest. These results support management to protect and recruit large snags well distributed across the landscape. The relatively high use of ponderosa pine and Gambel oak snags in both forest types suggests that recruitment of large pine and oak snags should be emphasized, and previous studies suggest emphasizing aspen recruitment as well. This may require special management efforts in mixed-conifer forest. These species are relatively shade-intolerant seral species in this forest type, and are apparently declining in this forest type due to fire-suppression efforts and resultant patterns of ecological succession. #
Sustaining Cavity-Using Species: Patterns of Cavity Use and Implications to Forest Management
ISRN Forestry, 2013
Many bird and mammal species rely on cavities in trees to rear their young or roost. Favourable cavity sites are usually created by fungi, so they are more common in older, dying trees that are incompatible with intensive fiber production. Forestry has reduced amounts of such trees to the extent that many cavity-using vertebrates are now designated “at risk.” The simple model of cavity use presented helps unite research findings, explain patterns of use, and clarify trade-offs that can, or cannot, be made in snag management. Predictions generated are tested using data from over 300 studies. Implications to forest management are derived from the tests, including the following: ensure sustained provision of dying and dead trees, retain both conifers and hardwoods and a range of size and age classes, sustain a range of decay classes, ensure that some large trees or snags are retained, promote both aggregated and dispersed retention of dead and dying trees, meet dead wood requirements f...
Prescribed fire, snag population dynamics, and avian nest site selection
Forest Ecology and Management, 2008
Snags are an important resource for a wide variety of organisms, including cavity-nesting birds. We documented snag attributes in a mixedconifer forest dominated by ponderosa pine in the Sierra Nevada, California where fire is being applied during spring. A total of 328 snags were monitored before and after fire on plots burned once, burned twice, or left unburned to assess the effects of prescribed fire on snag populations. The greatest loss of snags (7.1 snags ha À1 or 43%) followed the first introduction of fire after a long fire-free period. On plots burned a second time 21% of snags (3.6 snags ha À1 ) were lost, whereas 8% (1.4 snags ha À1 ) were lost on unburned control plots in the same time period. New snags replaced many of those lost reducing the net snag losses to 12% (2.0 ha À1 ) for plots burned once, and 3% (0.5 ha À1 ) for plots burned twice and unburned plots. We also examined snags used by cavity-nesting birds. Snags preferred for nesting were generally ponderosa pine (Pinus ponderosa), larger diameter, and moderately decayed as compared to available snags. For monitored snags that met the preferred criteria, there was a net loss (1.7 snag ha À1 or 34%) after the first burn, while the loss of useable snags was less than 1 snag ha À1 following the second burn (15%) or on unburned controls (8%). We recommend protection of preferred snags, in particular large ponderosa pines, especially during primary fire applications on fire-suppressed landscapes. Published by Elsevier B.V.
The standing dead: Importance of snags for cavity-nesting birds in tropical periurban forests
The Wilson Journal of Ornithology, 2023
Forested periurban areas represent a major asset for conservation as these sites could potentially mitigate the effects of landscape modification. Nevertheless, these forests face unsupervised management, affecting availability of resources such as tree cavities used by cavity-nesting vertebrates. We evaluated the ecological importance of snags for cavity-nesting birds in 3 periurban cloud forest remnants with different management regimes, degree of protection, and size in Veracruz, Mexico. We compared snag and cavity availability, traits, and density of primary and secondary cavity-nesting birds in 3 forested sites with different sizes and degree of disturbance. We found no snags and low cavity density in the smaller fragments, as well as lower species richness and density of cavity-nesting birds. Most suitable cavities were excavated by woodpeckers in snags, and were located in the largest forest remnant, where we also recorded the highest abundance of snags, excavators, and the highest richness of secondary cavity-nesters. Our results suggest a synergy of snag availability, primary excavators, and richness of secondary cavity-nesters in cloud forest fragments. Furthermore, simple actions, such as snag removal and/or firewood extraction, which are common activities in small forest fragments, can alter the composition of cavity-nesting assemblages with uncertain further ecological impacts.
Ecological Applications, 2012
Tree cavities are a vital multi-annual resource used by cavity-nesting birds and mammals for nesting and shelter. The abundance of this resource will be influenced by the rates at which cavities are created and destroyed. We applied the demographic concepts of survival and longevity to populations of tree holes to investigate rates of loss for cavities in three tree species, as well as how characteristics of nest trees, habitat type, and species of excavator affected the persistence of tree cavities in trembling aspen, Populus tremuloides (95% of cavities were in aspen trees), in interior British Columbia, Canada. By modeling survival of 1635 nesting cavities in aspen over a time span of 16 years, we found that the decay stage of the nest tree was the most important factor determining cavity longevity. Cavities in trees with advanced decay had a relatively short median longevity of 7 years (95% CI 6-9 years), whereas those in living trees had a median longevity of more than 15 years. We found that cavity longevity was greater in continuous forest than in aspen grove habitat. Interestingly, cavities formed by weak excavators survived as long as those created by Northern Flickers (Colaptes auratus), despite occurring in more decayed tree stems. Thus, weak excavators may be selecting for characteristics that make a tree persistent, such as a broken top. Our results indicate that retention of cavities in large, live aspen trees is necessary to conserve persistent cavities, and that cavity longevity will have a large effect on the structure and function of cavity-using vertebrate communities.