Arthropods are important prey for many avian taxa, particularly during the breeding season. Many studies have used sticky traps to estimate relative abundance of arthropods as avian prey, but we know little about the potential biases associated with sticky traps. We evaluated the effect of small-scale variation in trap placement on the biomass of arthropods caught on sticky traps in six riparian woodlands in southeastern Arizona. We detected differences in arthropod biomass between two height categories (1 and 4 m off the ground) for three insect orders and between two sampling locations (0 and 10 m from the center of the stream bed) for two insect orders. These differences indicate that placement of sticky traps affects arthropod capture rates and, hence, small variation in trap placement can bias investigators' ability to document spatial and temporal differences in arthropod abundance. Investigators who use sticky traps to make comparisons of arthropod abundance need to ensure that placement is consistent over time or across treatments to ensure that comparisons are not biased.

We attempted to collect diet samples using throat ligatures from nestlings of three songbird species in a riparian woodland in southeastern Arizona from May to August 2009. We had success with Song Sparrows (Melospiza melodia), observed adult Yellow-breasted Chats (Icteria sirens) reclaim food from nestlings, and discontinued the use of throat ligatures when we observed an adult Abert's Towhee (Pipilo aberti) remove two, 3-4-day-old ligatured nestlings from its nest. Previous studies have reported problems (e.g., aggression toward nestlings by adults) with throat ligatures, but we are the first to document removal (and subsequent nestling mortality) in response to this technique. We urge investigators to exercise caution when using throat ligatures on species for which evidence of the safety and efficacy of this method are lacking, especially when nestlings are small in size relative to adults. Received 18 February 2010. Accepted 29 April 2010.

We studied breeding populations of 2 coexisting ground-nesting birds, the red-faced warbler (Cardellina rubrifrons) and yellow-eyed junco (Junco phaeonotus), in high-elevation (>2,000 m) forested drainages of the Santa Catalina Mountains, Arizona, USA. From 2004 to 2005, we 1) estimated density and nesting success of breeding populations of red-faced warblers and yellow-eyed juncos, 2) identified nest-site characteristics for each species (i.e., used sites vs. random plots), 3) compared nest-site characteristics between the 2 species, and 4) examined effects of a recent (2003) wildfire on distribution of nests of both species. In addition, we estimated the areal extent of montane riparian forest (the preferred breeding habitat of both species) within high-elevation forests of the Santa Catalina Mountains. We found that red-faced warblers and yellow-eyed juncos were the 2 most common ground-nesting birds within our study area with an average density of 2.4 and 1.4 singing males/ha, respectively, along drainage bottoms. Compared to random plots, most red-faced warbler and yellow-eyed junco nests were located close (<= 30 m) to drainage bottoms within a strip of montane riparian forest characterized by abundant brush, small woody debris, ferns, and forbs (both species), high number and diversity of saplings and small trees (red-faced warblers), and abundant shrubs and downed logs and less canopy cover (yellow-eyed juncos). Although both species nested in close proximity within montane riparian forest, nest-site characteristics differed between the 2 species, especially at finer spatial scales. For example, most yellow-eyed juncos nested adjacent to grass (principally Muhlenbergia spp.), whereas red-faced warblers nested adjacent to a variety of plant species, including grass, bigtooth maple (Acer grandidentatum), white fir (Abies concolor), and Douglas-fir (Pseudotsuga menziesii). Both red-faced warblers and yellow-eyed juncos avoided nesting in areas burned during a recent wildfire. In addition, nesting success was low for red-faced warblers (13%) and yellow-eyed juncos (19%) following the wildfire, suggesting an indirect negative effect of fire on breeding populations in the short-term. Montane riparian forest appears to provide important breeding habitat for red-faced warblers and yellow-eyed juncos. However, little research or conservation planning has been directed toward montane riparian forest in the region, even though this forest type is limited in its areal extent (<11% of high-elevation forest in the Santa Catalina Mountains) and increasingly threatened by disturbance. Results from our study can be used to facilitate the management and conservation of breeding populations of red-faced warblers and yellow-eyed juncos in high-elevation forests of the southwestern United States.

We used time-lapse video cameras and track plates to identify nest predators of Red-faced Warblers (Cardellina rubrifrons) and Yellow-eyed Juncos (Junco phaeonotus) in high-elevation (> 2,300 m) forests of the Santa Catalina Mountains in southeastern Arizona. Mammals, especially gray fox (Urocyon cinereoargenteus) and cliff chipmunk (Tamias dorsalis), were the principal nest predators of Red-faced Warblers and Yellow-eyed Juncos within our study system, accounting for 89% of all nest depredations. Our study is one of the first to use video cameras at real nests to document the prevalence of nest predators in montane forest ecosystems. Additional research is needed to learn if mammals are the dominant nest predators in other montane environments. Received 23 October 2009. Accepted 24 March 2010.

Parent birds of many altricial species remove nestling excrement (Blair 1941), eggshells (Montevecchi 1974), foreign debris (e.g. rings on nestlings; Berger 1953), ecto-parasites (Hurtrez-Bousses et al. 2000) and dead nestlings (Skutch 1976) from their nests; a set of behaviours collectively known as nest sanitation (Welty 1982). When sanitizing a nest of dead nestlings, parent birds typically remove a single dead nestling from a nest that contains other live nestlings (Payn 1966, Davis 1967), thus modifying slightly the contents of the nest. Observations of nest contents by field personnel are often used to infer nest fates (e.g. depredated, abandoned). For example, standard nest-monitoring protocols dictate that nests found empty and intact (i.e. nest cup and lining undisturbed) well before the anticipated fledge date are likely to have been depredated (Martin & Geupel 1993, Ralph et al. 1993). We provide evidence that an empty, intact nest may not always indicate a nest depredation, but instead may result from the sanitation of an entire brood of dead nestlings by parent birds following complete brood mortality (probably caused by inclement weather or starvation). Sanitation of entire broods of dead nestlings by parent birds is unreported in the literature and has implications for nest-monitoring studies that estimate cause-specific nest failure rates (Etterson et al. 2007). We observed this behaviour while monitoring breeding populations of Red-faced Warblers Cardellina rubrifrons and Yellow-eyed Juncos Junco phaeonotus in the Santa Catalina Mountains, Pima County, Arizona, USA. Red-faced Warblers and Yellow-eyed Juncos are monogamous, ground-nesting birds that breed in montane forests of the southwestern USA and Mexico (Martin & Barber 1995, Sullivan 1999, Corman & Wise-Gervais 2005). Within the Santa Catalina Mountains, both species breed concurrently (late April to early July), have similar incubation and nestling period lengths (approximately 25 days combined) and select similar nest-sites (Martin & Barber 1995, Sullivan 1999, C. Conway & C. Kirkpatrick unpubl. data). Red-faced Warblers have a modal clutch and brood size of four, whereas Yellow-eyed Juncos have a modal clutch size of four and a modal brood size of three (C. Conway & C. Kirkpatrick unpubl. data). Nest depredation accounts for > 90% of all nest failures and Gray Fox Urocyon cinereoargenteus (an olfactory predator) is one of the principal nest predators of both species (C. Conway & C. Kirkpatrick unpubl. data). During the 2006 breeding season, we located and monitored 76 Red-faced Warbler and 76 Yellow-eyed Junco nests on five 16–20-ha study sites within high-elevation (2367 m to 2791 m asl) forests of the Santa Catalina Mountains using standard nest-monitoring methods (Martin & Geupel 1993). We briefly visited each nest every 2–3 days to check nest status. We recorded nest status as active if we observed (from a distance) parent birds on or in the immediate vicinity of nests and we approached nests to verify nest status and nest contents if parent birds were absent (sensu Martin et al. 2000). We assumed that a nest had been depredated when eggs or nestlings were missing (Martin & Geupel 1993, Ralph et al. 1993, Martin 1998). We used a protocol modified from McQuillen and Brewer (2000) to monitor continuously a subset of nine Red-faced Warbler and nine Yellow-eyed Junco nests using time-lapse video cameras equipped with infrared illumination for night-time photography (henceforth ‘video cameras’; Fieldcam TLV, Fuhrman Diversified Inc., Seabrook, Texas, USA). When we checked video camera nests in the field and found that they had been depredated (or so we assumed), we continued video-taping at the nests for 24 h before dismantling the video cameras and reviewing video tapes to determine the exact cause of the nest failures. While monitoring nests with video cameras in July 2006, we observed two instances in which parent birds sanitized nests by removing their entire brood following the apparent death of the nestlings. In the first instance, video footage showed a female Yellow-eyed Junco brooding two 1-day-old nestlings (and incubating one apparently infertile egg) during the morning of 5 July 2006 at a nest located near the summit of Mt. Lemmon, the highest point in the Santa Catalina Mountains. At 8:17 h, the brooding female sat up and began pecking vigorously at the nestlings (presumably to check if the nestlings were still alive). The female continued to peck at the nestlings for approximately 180 s before flying away from the nest carrying a nestling in her bill. At 8:30 h, a parent bird returned to the nest and removed the second nestling after pecking at it for approximately 25 s (Fig. 1). A field observer checked the contents of the nest at 12:15 h, found the nest with only one egg and recorded that the nest had been partially depredated. The field observer also noted that the nest cup and lining were intact. Video footage revealed that the parent birds made several visits to check the nest or to sit on the remaining egg from 8:30 h to 18:05 h, at which point the parent birds abandoned the nest. Still image from video footage taken on 5 July 2006 showing a female Yellow-eyed Junco Junco phaeonotus removing the second of two nestlings that died following a strong thunderstorm on 4 July 2006 in the Santa Catalina Mountains, Arizona, USA. Date and time are indicated in the upper left corner of frame. In the second instance, video footage showed a female Red-faced Warbler brooding and feeding (on one occasion only) three 4-day-old nestlings during the morning of 6 July 2006 at a nest located in Marshall Gulch, 3 km southeast of the summit of Mt. Lemmon. This activity ended at 10:27 h when the female left the nest. A parent bird returned to the nest at 15:11 h (almost 5 h after the last visit), at which point the parent bird pecked vigorously at the nestlings for approximately 60 s. The parent bird flew away from the nest carrying what appeared to be nestlings in its bill at 15:14 h and again at 15:23 h (we observed only two trips away from the nest, but believe that the parent bird carried away all three nestlings during these two trips). Video footage revealed that the parent bird never returned to the nest and the nest remained undisturbed by nest predators until a field observer checked the contents of the nest at 12:36 h on 7 July 2006. The field observer found the nest empty and recorded that it had been depredated. The field observer also noted that the nest cup and lining were intact. Both the Red-faced Warbler and Yellow-eyed Junco nests failed 1–2 days after a series of strong thunderstorms dropped an average of 63 mm of precipitation across our study sites between approximately 13:00 h on 4 July 2006 and 13:00 h on 6 July 2006 (Fig. 2; Mt. Lemmon and Marshall Gulch weather stations, Pima County 2006). The precipitation recorded during this 48-h period was substantial (accounting for 9% of the 681 mm average annual precipitation total; Brown 1994) and marked the beginning of the summer monsoon. Moreover, ambient temperature declined substantially during the thunderstorms: for example, ambient temperature fell from 19 °C to 12 °C at the start of the first major thunderstorm on the afternoon of 4 July 2006 (Mt. Lemmon weather station, University of Utah 2007). Rainfall totals (mm) taken between 6:00 h on 4 July 2006 and 24:00 h on 7 July 2006 at the Mt. Lemmon (dashed line) and Marshall Gulch (solid line) weather stations, Santa Catalina Mountains, Arizona, USA (Pima County 2006). The two arrows indicate the times and dates that parent birds were observed (on video tape) sanitizing nests of all dead nestlings at a Red-faced Warbler nest located in Marshall Gulch, and at a Yellow-eyed Junco nest located near the summit of Mt. Lemmon. Rainfall data were collected hourly at both weather stations (Pima County 2006). Although the female Yellow-eyed Junco initially brooded her nestlings during the thunderstorm on 4 July 2006, she abandoned the nest after only 25 min when the nest became partially flooded by hail and rain (evident on video footage). We believe the Yellow-eyed Junco nestlings probably drowned or died from hypothermia shortly after the thunderstorm began because of the quantity of hail and rain that accumulated around the nest, the attendant decrease in ambient temperature, the absence of the brooding female, and the young age (1 day) of the nestlings. Moreover, the nestlings were unresponsive to subsequent feeding attempts by the male Yellow-eyed Junco immediately following the storm. Inclement weather can lead to complete brood mortality (Stewart 1972, Imanishi 2007) and young, altricial nestlings are especially vulnerable to cold because of their inability to thermoregulate (Dunn 1975). We speculate that the Red-faced Warbler nestlings died from some combination of starvation and hypothermia. After the nestlings hatched on the afternoon of 2 July 2006, video footage showed only one parent (presumably the female) feeding and brooding nestlings, suggesting that the male died or abandoned the nest prior to the hatch date. Although the female fed and brooded the nestlings during the 48-h period of inclement weather, she took long off-bouts from the nest between thunderstorms, culminating with an off-bout of almost 5 h just before the nestlings died and the nest was sanitized. We cannot say to what extent the thunderstorms contributed to the death of the nestlings, but we believe that the inclement weather likely hastened the failure of the nest. Inclement weather can inhibit foraging by adult birds, potentially reducing their ability to survive (as suggested in Boyle 2006) and provision young (Stewart 1972, Kepler et al. 1996). In general, nest sanitation is thought to be an adaptive behaviour that has evolved to limit infestations by nest parasites (Silver 1977), reduce egg-capping by stray eggshells (Montevecchi 1974, Derrickson & Warkentin 1991), provide supplemental nutrition for parent birds (e.g. ingestion of faecal sacs; Morton 1979) or reduce the potential of nest depredation (Tinbergen et al. 1963, Silver 1977). For example, the removal of a dead nestling from a nest following a partial brood mortality may serve to reduce the risk of nest depredation by olfactory predators during the current nesting attempt. In a similar manner, parent Red-faced Warblers and Yellow-eyed Juncos observed during the current study may have removed entire broods of dead nestlings from their nests following complete brood mortalities to reduce the probability of nest depredation by olfactory predators during subsequent nesting attempts within their breeding territories. In contrast, sanitation of entire broods of dead nestlings by parent birds may result from an innate behavioural program that is triggered by an environmental stimulus (e.g. a dead nestling) and, once started, is carried through to completion (i.e. an empty nest; Gould 1982). However, we observed three instances during 5 years of nest monitoring in which complete brood mortality following inclement weather did not result in the sanitation of dead nestlings by parent Red-faced Warblers (C. Conway & C. Kirkpatrick unpubl. data), suggesting that the behaviour varies among individuals. This variation could be based on differences in the age or experience level of breeding birds (Gould 1982) or differences in the spatial or temporal risk of nest depredation by olfactory predators. Further research is needed to examine the underlying cause(s) of sanitation of entire broods of dead nestlings by parent birds, the extent of variation in this behaviour, and the factors that predict its occurrence. Given that complete brood mortality is a prerequisite for sanitation of entire broods of dead nestlings, we suggest that researchers pay particular attention to assigning fates to empty, intact nests during times when the risk of complete brood mortality is high. For example, complete brood mortality is more likely to occur: (1) in areas that experience bouts of inclement weather (Stewart 1972, Imanishi 2007), (2) at nests that are prone to flooding (e.g. ground nests; Shriver et al. 2007) and (3) when nestlings are young and susceptible to hypothermia (Dunn 1975). In addition to weather-related nest failures, complete brood mortality is more likely to occur as a result of starvation: (1) in environments where food resources are limited or highly variable (Bensch 1992), (2) when one parent is killed or abandons a nest (Duckworth 1992) and (3) in polygynous species in which males must partition their time among multiple nests (Dyrcz 1986, Johnson et al. 1993, but see Urano 1992). Subsequent sanitation of entire broods of dead nestlings following complete brood mortality is likely to vary among and even within species (as evidenced by Red-faced Warblers in the current study). Therefore, researchers should endeavour to estimate the relative frequency with which this behaviour occurs on a species-by-species basis to avoid classification errors in assigning nest fates. The probability that a researcher will witness a parent bird removing a dead nestling from a nest is remote (Mayer-Gross 1966). However, researchers can improve their odds of witnessing such events by checking nests frequently (assuming increased nest checks do not adversely affect nesting success; Etterson et al. 2007) or by employing video cameras at nests (as in the current study; Pierce & Pobprasert 2007) following events that increase the probability of complete brood mortality. Data collected in this manner should allow researchers to reduce bias in cause-specific nest failure rates resulting from the misclassification of nest fates. In the meantime, researchers should use caution when assigning fates to empty, intact nests and not assume that nest depredation is the sole cause of these nest failures. We thank M. Eastwood, N. Nardello and T. Selvidge for assistance locating nests and operating video cameras and S. Sferra (U.S. Bureau of Reclamation) for supplying video cameras. R. Peterson and the University of Arizona Steward Observatory provided field housing. T. Harrison, J. Reynolds, J. Smith and two anonymous reviewers provided helpful comments on earlier versions of this paper. Funding was provided by the U.S. Fish and Wildlife Service, the U.S. Geological Survey and T & E, Inc.

: Riparian woodlands in the desert southwest are an extremely important resource because they constitute 50% of the breeding birds. Riparian woodlands also provide shelter and critical food resources for dozens of species of Neotropical migratory birds that alight in these woodlands during their spring and fall migrations across the desert southwest. Ground water withdrawal (and subsequent loss of surface water) to support urban developments in the desert southwest has the potential to degrade or eliminate riparian woodlands throughout the region, including riparian woodlands along the Upper San Pedro River adjacent to Fort Huachuca Military Reservation in Arizona. Military readiness could be jeopardized if limited military resources are diverted from the military's mission at Fort Huachuca Military Reservation (and at other military installations in the southwestern U.S.) to deal with the recovery of potentially dozens of declining populations of birds. The objective of this ongoing research project is to assess the value of riparian woodlands to the health and persistence of avian communities in the desert southwest. Specifically, we seek to quantify the extent to which both surface water and the health of riparian vegetation influence the abundance and diversity of riparian birds in the region. From March to September 2006 and 2007, we surveyed birds, sampled vegetation, and measured surface water at 23 study sights located in riparian woodlands throughout southeastern Arizona, including several study sites situated along the Upper San Pedro River near Fort Huachuca Military Reservation. We also sampled avian food resources (i.e., aerial arthropods) and monitored nests of riparian bird species at a subset of these study sites.

ABSTRACT Buff‐breasted flycatchers ( Empidonax fulvifrons ) are rare in the United States due to a >90% reduction in breeding distribution. Previous authors have implicated fire suppression in montane woodlands as the underlying cause of population declines and range contraction. We examined the effect of fire suppression on population declines of buff‐breasted flycatchers by comparing both presence and abundance of flycatchers in areas with and without evidence of recent fire in 9 mountain ranges in southern Arizona, USA. We also replicated previous survey efforts conducted in 1980–1983 and 1995–1996 to determine population trajectory. Twenty‐two (63%) of 35 survey routes had negative trends, and the average slope of the declines was −0.105 (10.5% annual decline). The number of buff‐breasted flycatchers detected at a survey point was positively associated with severity of recent fires, and flycatchers were particularly associated with areas that had evidence of high‐severity surface fire. However, we failed to detect flycatchers in 5 canyons that recently burned, which suggests one or more of the following: 1) fire suppression is not the cause (or is not the main cause) of population decline and range contraction, 2) flycatchers do not colonize burned areas until >10 years postfire, 3) low‐ or medium‐severity fires are insufficient to make fire‐suppressed areas suitable for breeding flycatchers, or 4) local recruitment and immigration are insufficient to allow buff‐breasted flycatchers to expand into recent firerestored areas. Continued suppression of high‐severity forest fires in the southwestern United States may eventually result in the extirpation of buff‐breasted flycatchers. A landscape that includes a mosaic of recently burned and unburned forest patches appears to be most suitable for buff‐breasted flycatchers. Prescribed burning is unlikely to help restore flycatcher populations unless burns are of high severity, conditions typically avoided during prescribed burns for safety reasons.

We detected buff-breasted flycatchers (Empidonax fulvifrons) while conducting surveys in the Rincon Mountains, Arizona, in 2000 (n = 2), 2004 (n = 4), and 2005 (n = 5). Our detections represent the first records of buff-breasted flycatchers in the Rincon Mountains since 1911, suggesting that this rare species has recolonized a portion of its historical breeding range.

Estimates of population trend for the interior subspecies of band-tailed pigeon (Patagioenas fasciata fasciata) are not available because no standardized survey method exists for monitoring the interior subspecies. We evaluated 2 potential band-tailed pigeon survey methods (auditory and call-broadcast surveys) from 2002 to 2004 in 5 mountain ranges in southern Arizona, USA, and in mixed-conifer forest throughout the state. Both auditory and call-broadcast surveys produced low numbers of cooing pigeons detected per survey route (x <= 0.67) and had relatively high temporal variance in average number of cooing pigeons detected during replicate surveys (CV >= 161%). However, compared to auditory surveys, use of call-broadcast increased 1) the percentage of replicate surveys on which >= 1 cooing pigeon was detected by an average of 16%, and 2) the number of cooing pigeons detected per survey route by an average of 29%, with this difference being greatest during the first 45 minutes of the morning survey period. Moreover, probability of detecting a cooing pigeon was 27% greater during call-broadcast (0.80) versus auditory (0.63) surveys. We found that cooing pigeons were most common in mixed-conifer forest in southern Arizona and density of male pigeons in mixed-conifer forest throughout the state averaged 0.004 (SE = 0.001) pigeons/ha. Our results are the first to show that call-broadcast increases the probability of detecting band-tailed pigeons (or any species of Columbidae) during surveys. Call-broadcast surveys may provide a useful method for monitoring populations of the interior subspecies of band-tailed pigeon in areas where other survey methods are inappropriate.

The frequency of wild and prescribed fires in montane forests of the southwestern United States has increased after a century of fire suppression and subsequent fuels accumulation. To assess the effects of recent fires (median time since fire = 6 yr) on the montane forest bird community, we surveyed birds in 8 Sky Island mountain ranges in southeastern Arizona, USA, and examined how the distribution (i.e., presence-absence) of 65 species and relative abundance of 16 species correlated with evidence of severe and less severe fire at > 1,500 survey points. We detected associations between fire and bird presence-absence for 17% of the 65 species analyzed and between fire and bird relative abundance for 25% of the 16 species analyzed. Most species (73%) were positively associated with burned areas and displayed stronger associations (i.e., more extreme odds ratios) with survey points that had evidence of severe as opposed to less severe fire. Positive associations with severe fire were strong (> 3 to 1 odds) for western wood-pewee (Contopus sordidulus) and house wren (Troglodytes aedon), and negative associations with severe fire were strong for warbling vireo (Vireo gilvus) and red-breasted nuthatch (Sitta canadensis). Although recent fires appear to have had a positive effect on the distribution and relative abundance of several montane forest bird species in the region, these species are not the open-woodland birds that we would have expected to have benefited from fire based on previous research. Nevertheless, our results confirm associations between fire and bird presence-absence and relative abundance reported previously for 7 species of birds. Our results also provide new information for Grace's warbler Dendroica graciae) and greater pewee (C. pertinax), 2 species for which fire data were formerly lacking. Managers can use these data to make and test predictions about the effects of future fires, both severe and less severe, on montane forest birds in the southwestern United States.

The ability of Rieke zinc to reduce common organic functional groups has been studied. Nitrobenzene, conjugated aldehydes, arylacetylenes, and phenylpropiolates are readily reduced under mild conditions. Benzonitrile, alkylacetylenes, ketones, unconjugated aldehydes, and alkenes are not reduced.

While monitoring songbird nests using video cameras in May 2005, we documented a woodrat (Neotoma) depreciating an adult female and nestling yellow-eyed junco (Junco phaeonotus) in the Santa Catalina Mountains, Arizona. Based on elevation (2,750 m) and the forest type surrounding the depredated nest, we believe that the woodrat was probably N. mexicana (although we cannot exclude N. albigula). Woodrats are considered herbivorous and have never been observed depreciating vertebrate prey. This observation demonstrates that woodrats have greater dietary plasticity than previously thought.

We examined short-term trends in relative abundance and species richness of breeding and wintering grassland birds before (1996) and after (1997, 1998) a prescribed burn in a mesquite-invaded, desert grassland at Buenos Aires National Wildlife Refuge, Arizona. We surveyed birds and sampled vegetation along 1-km line transects bisecting 14 (7 control, 7 burn) 25-ha Plots located randomly within a burn and adjacent, control unit. Following a spring burn that was moderate in intensity and patchy ill areal extent, we observed that ground Cover was affected more strongly by burning than mesquite (Prosopis) cover, smaller mesquite were affected more strongly by burning than larger mesquite, and mortality of mesquite was low. No change in total abundance of birds was detected oil the burn unit following fire for either wintering or breeding birds; however, species richness of breeding birds decreased in the first war post-burn. During the breeding season, mourning doves (Zenaida macroura) increased, whereas Botteri's sparrows (Aimophila botterii), Cassin's sparrows (Aimophila and cassinii), and (Campylorhynchus brunneicapillus) decreased in relative abundance following fire. During the wintering season, ladder-backed woodpeckers (Picoides scalaris) and vesper sparrows (Pooeceles gramineus) increased and cactus wrens decreased in relative abundance following fire. Beyond species-level trends, we found stronger evidence of trends and greater magnitudes of relative change for breeding species associated with open grasslands compared to those associated with shrubs. The use of spring burns on the Refuge will likely improve conditions for open-grassland species that were historically more abundant by killing smaller mesquite and reducing mesquite recruitment. However, more intense and extensive fires will be required to reduce the presence of larger mesquite. Such fires would likely have a greater impact oil birds associated with shrubs, and consequently, a greater impact oil the avian community as a whole.

In 2008, Units scientists and their cooperators advanced the mission of the CRU Program through joint research, education, technical assistance, and science support. Unit sci- entists continued to be very productive in 2008, completing a number of projects for federal (94) and state (135) partners. Unit scientists and their students remained actively engaged in service to professional societies delivering over 600 presentations. Many of these presentations were invited seminars, indicating that Unit scientists and their research are held in high regard by the scientifi c and management communities. CRU's service to university cooperators continued to be strong, with 75 academic classes taught in 2008 and an additional 46 workshops and short courses delivered to partners and cooperators. Staffi ng and Trends in Productivity CRU partially restored its science capacity in 2008, and several hiring actions have been initiated in 2009 to fi ll positions vacated through retirements. However, the program continues to sustain over 20 vacant scientist positions at Units across the country. Some concerns related to staffi ng include declines in 2007 and 2008 in the number of master's and doctoral students graduating each year. However, a trend for decreasing numbers of federal projects corresponds with an increase in the number of state projects, so the eff ects of reduced staffi ng are not entirely clear. A priority will continue to be to deliver products and science support services that are important to cooperators.